diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..ce8530f
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "utils"
+version = "0.1.0"
diff --git a/src/combination.rs b/src/combination.rs
new file mode 100644
index 0000000..4bd05e6
--- /dev/null
+++ b/src/combination.rs
@@ -0,0 +1,104 @@
+use std::error::Error;
+
+fn factorial(num: usize) -> usize {
+    let mut fact = 1;
+    for n in 1..=num {
+        fact *= n;
+    }
+    fact
+}
+
+fn binomial(n: usize, k: usize) -> usize {
+    if k > n {
+        0
+    } else {
+        factorial(n) / (factorial(k) * factorial(n - k))
+    }
+}
+
+#[derive(Clone)]
+pub struct Combinator<T: Clone + Ord> {
+    pub current: Vec<T>,
+    pub k: usize,
+    idx: usize,
+}
+
+impl<T: Clone + Ord> Combinator<T> {
+    pub fn new(elements: Vec<T>, k: usize) -> Result<Combinator<T>, Box<dyn Error>> {
+        if k > elements.len() || k == 0 {
+            return Err(Box::from("Out of bounds"));
+        }
+        Ok(Self {
+            current: elements,
+            k,
+            idx: 0,
+        })
+    }
+
+    pub fn nth_lex(mut elements: Vec<T>, k: usize, nth: usize) -> Result<Vec<T>, Box<dyn Error>> {
+        elements.sort();
+        let num_elements = elements.len();
+        let num_combinations = binomial(num_elements, k);
+        if nth > num_combinations || k > num_elements || nth == 0 || k == 0 {
+            return Err(Box::from("Out of bounds"));
+        }
+        let mut i = 0;
+        let mut remaining_k = k;
+        let mut comb = Vec::new();
+        let mut remainder = nth - 1;
+        while remaining_k > 0 {
+            // Count the number of combinations that start with elements[i]
+            // example with n = 5, k = 2
+            // nth <= 4 select first
+            // nth <= 7 select second
+            // nth <= 9 select third
+            // nth == 10 select fourth
+            let count = binomial(num_elements - i - 1, remaining_k - 1);
+            if remainder < count {
+                // If the nth combination is within the count, pick this element
+                comb.push(elements[i].clone());
+                remaining_k -= 1;
+            } else {
+                remainder -= count;
+            }
+            i += 1;
+        }
+        Ok(comb)
+    }
+}
+
+impl<T: Clone + Ord> Iterator for Combinator<T> {
+    type Item = Vec<T>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let num_elements = self.current.len();
+        let num_combinations = binomial(num_elements, self.k);
+        if self.idx == num_combinations {
+            return None;
+        }
+        let mut i = 0;
+        let mut remaining_k = self.k;
+        let mut comb = Vec::new();
+        let mut remainder = self.idx - 1;
+        while remaining_k > 0 {
+            // Count the number of combinations that start with elements[i]
+            // example with n = 5, k = 2
+            // nth <= 4 select first
+            // nth <= 7 select second
+            // nth <= 9 select third
+            // nth == 10 select fourth
+            let count = binomial(num_elements - i - 1, remaining_k - 1);
+            if remainder < count {
+                // If the nth combination is within the count, pick this element
+                comb.push(self.current[i].clone());
+                remaining_k -= 1;
+            } else {
+                remainder -= count;
+            }
+            i += 1;
+        }
+        self.idx += 1;
+        self.current = comb;
+        Some(self.current.clone())
+    }
+}
diff --git a/src/grid.rs b/src/grid.rs
new file mode 100644
index 0000000..ff76b51
--- /dev/null
+++ b/src/grid.rs
@@ -0,0 +1,33 @@
+use std::error::Error;
+
+#[derive(Debug)]
+pub struct Grid<T: Clone>(pub Vec<Vec<T>>);
+
+impl<T: Clone> Grid<T> {
+    pub fn new(grid: Vec<Vec<T>>) -> Result<Self, Box<dyn Error>> {
+        let row_length = grid[0].len();
+        for row in &grid {
+            if row_length != row.len() {
+                return Err(Box::from("Rows need to all be equal in length"));
+            }
+        }
+        Ok(Grid(grid))
+    }
+
+    pub fn invert(&mut self) -> Self {
+        let height = self.0.len();
+        let width = self.0[0].len();
+
+        let mut new_grid = Vec::with_capacity(width);
+
+        for col_idx in 0..width {
+            let mut new_row = Vec::with_capacity(height);
+            for row_idx in 0..height {
+                new_row.push(self.0[row_idx][col_idx].clone());
+            }
+            new_grid.push(new_row);
+        }
+        self.0 = new_grid;
+        Grid(self.0.clone())
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..40ccb35
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,5 @@
+pub mod combination;
+pub mod grid;
+pub mod math;
+pub mod number;
+pub mod permutation;
diff --git a/src/main.rs b/src/main.rs
deleted file mode 100644
index e7a11a9..0000000
--- a/src/main.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-fn main() {
-    println!("Hello, world!");
-}
diff --git a/src/math.rs b/src/math.rs
new file mode 100644
index 0000000..1a0fb80
--- /dev/null
+++ b/src/math.rs
@@ -0,0 +1,74 @@
+use std::collections::HashSet;
+
+pub fn prime_factors(number: u64) -> Vec<u64> {
+    let mut factors = vec![2];
+    let upper: u64 = (number as f64).sqrt().ceil() as u64;
+    for i in 3..upper {
+        let mut is_prime = true;
+        for factor in &factors {
+            if i % factor == 0 {
+                is_prime = false;
+                break;
+            }
+        }
+        if is_prime && number % i == 0 {
+            factors.push(i);
+        }
+    }
+
+    factors
+}
+
+pub fn nth_prime(nth: i64) -> Option<i64> {
+    let mut primes: Vec<i64> = vec![2];
+
+    let mut i = 3;
+
+    while primes.len() < nth as usize {
+        let mut is_prime = true;
+        for prime in &primes {
+            if i % prime == 0 {
+                is_prime = false;
+                break;
+            }
+        }
+        if is_prime {
+            primes.push(i);
+        }
+        i += 1;
+    }
+
+    primes.pop()
+}
+
+pub fn factorial(n: u64) -> u64 {
+    let mut result = 1;
+    for i in 1..=n {
+        result *= i;
+    }
+    result
+}
+
+pub fn get_divisors(n: u64) -> Vec<u64> {
+    let mut divisors = HashSet::from([1]);
+    let mut potential_divisor = 2;
+    while (potential_divisor * potential_divisor) <= n {
+        if n % potential_divisor == 0 {
+            divisors.insert(potential_divisor);
+            divisors.insert(n / potential_divisor);
+        }
+        potential_divisor += 1;
+    }
+    divisors.iter().copied().collect()
+}
+
+pub fn fib(n: u64) -> u64 {
+    let mut last_two = (1, 1);
+    let mut iteration = 1;
+    while iteration < n {
+        last_two = (last_two.1, last_two.0 + last_two.1);
+        iteration += 1;
+    }
+
+    last_two.0
+}
diff --git a/src/number.rs b/src/number.rs
new file mode 100644
index 0000000..cf4ecfc
--- /dev/null
+++ b/src/number.rs
@@ -0,0 +1,423 @@
+use std::cmp::{min, Ordering};
+use std::fmt::{Display, Formatter};
+use std::iter::zip;
+use std::ops::{Add, Div, Mul, Rem, Sub};
+
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+pub enum Sign {
+    Positif,
+    Negatif,
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+pub struct Number {
+    pub digits: Vec<isize>,
+    pub sign: Sign,
+}
+
+impl Number {
+    pub fn get_digit(n: isize, pos: usize) -> isize {
+        let modulo = 10isize.pow(pos as u32 + 1);
+        let divisor = modulo / 10;
+        (n % modulo) / divisor
+    }
+
+    pub const fn byte_to_digit(b: u8) -> isize {
+        // wrapping_sub('0' as u32) same as - 48 but less magical
+        (b as isize).wrapping_sub('0' as isize)
+    }
+
+    fn handle_overflows(&mut self) {
+        let new_digits = &mut self.digits;
+        let digits_len = new_digits.len();
+        let mut digits_idx = digits_len - 1;
+        loop {
+            let digit_or_num = new_digits[digits_idx];
+            let digit_len = if digit_or_num != 0 {
+                (digit_or_num.abs() as f64 + 1.0).log10().ceil() as usize
+            } else {
+                1
+            };
+            for i in 0..digit_len {
+                let new_digit = Self::get_digit(digit_or_num, i);
+                let (digit_idx, is_overflow) = digits_idx.overflowing_sub(i);
+                if is_overflow {
+                    new_digits.insert(0, new_digit);
+                    digits_idx += 1;
+                } else {
+                    let digit = new_digits.get_mut(digit_idx).unwrap();
+                    if i == 0 {
+                        *digit = new_digit;
+                    } else {
+                        *digit += new_digit;
+                    }
+                }
+            }
+            if digits_idx == 0 {
+                break;
+            }
+            digits_idx -= 1;
+        }
+    }
+
+    fn handle_underflows(&mut self) {
+        let new_digits = &mut self.digits;
+        let mut digits_len = new_digits.len();
+        for digit in new_digits.clone() {
+            match digit.cmp(&0) {
+                Ordering::Equal => {
+                    if digits_len == 1 {
+                        return;
+                    }
+                    digits_len -= 1;
+                    new_digits.remove(0);
+                }
+                Ordering::Less => {
+                    self.sign = Sign::Negatif;
+                    break;
+                }
+                _ => break,
+            };
+        }
+        let mut digits_idx = digits_len - 1;
+        loop {
+            let digit = new_digits[digits_idx];
+            if self.sign == Sign::Positif && digit < 0 && digits_idx > 0 {
+                let mut_digit = new_digits.get_mut(digits_idx).unwrap();
+                *mut_digit = 10 - digit.abs();
+                let mut_digit = new_digits.get_mut(digits_idx - 1).unwrap();
+                *mut_digit -= 1;
+            } else {
+                let mut_digit = new_digits.get_mut(digits_idx).unwrap();
+                *mut_digit = digit.abs();
+            }
+            if digits_idx == 0 {
+                break;
+            }
+            digits_idx -= 1;
+        }
+        for digit in new_digits.clone() {
+            match digit.cmp(&0) {
+                Ordering::Equal => {
+                    new_digits.remove(0);
+                }
+                _ => break,
+            };
+        }
+    }
+
+    pub fn pow(self, n: u32) -> Self {
+        let mut result = self.clone();
+        if ((self.digits.len() * 8) as u32) < isize::BITS {
+            let number = isize::from(self);
+            for _i in 1..n {
+                result = result * number;
+            }
+            result
+        } else {
+            let number = self.clone();
+            for _i in 1..n {
+                result = result * number.clone();
+            }
+            result
+        }
+    }
+
+    pub fn fact(self) -> Self {
+        let mut fact = Number::from(1);
+        if ((self.digits.len() * 8) as u32) < isize::BITS {
+            let max = isize::from(self);
+            for n in 1..=max {
+                fact = fact * n;
+            }
+            fact
+        } else {
+            panic!("starting number too big")
+        }
+    }
+
+    pub fn fib(n: u64) -> Self {
+        let mut last_two = (Self::from(1), Self::from(1));
+        let mut iteration = 1;
+        while iteration < n {
+            last_two = (last_two.1.clone(), last_two.0 + last_two.1);
+            iteration += 1;
+        }
+
+        last_two.0
+    }
+
+    fn div_with_rem(n1: Number, n2: Number) -> (Number, Number) {
+        let n1_len = n1.digits.len();
+        let n2_len = n2.digits.len();
+        if n2_len > n1_len {
+            return (Number::from(0), n2);
+        }
+        let dividend = n1.digits[..n2_len].to_vec();
+        let mut quotient = vec![];
+        let mut remainder = Number {
+            digits: dividend.clone(),
+            sign: Sign::Positif,
+        };
+        let mut iteration = 1;
+        loop {
+            let mut factor = 0;
+            loop {
+                let temp_remainder = remainder.clone() - n2.clone();
+                if temp_remainder.sign == Sign::Negatif {
+                    quotient.push(factor);
+                    break;
+                }
+                remainder = temp_remainder;
+                factor += 1;
+            }
+            if n1_len == n2_len + iteration - 1 {
+                break;
+            }
+            remainder.digits.push(n1.digits[n2_len + iteration - 1]);
+            iteration += 1;
+        }
+        let mut res = Number {
+            digits: quotient,
+            sign: Sign::Positif,
+        };
+        res.handle_overflows();
+        for digit in res.clone().digits {
+            if digit != 0 {
+                break;
+            }
+            res.digits.remove(0);
+        }
+        for digit in remainder.clone().digits {
+            if digit != 0 || remainder.digits.len() == 1 {
+                break;
+            }
+            remainder.digits.remove(0);
+        }
+        (res, remainder)
+    }
+}
+
+impl From<Number> for isize {
+    fn from(value: Number) -> Self {
+        let mut num = 0;
+        for (pos, &digit) in value.digits.iter().rev().enumerate() {
+            num += digit * 10isize.pow(pos as u32);
+        }
+        num
+    }
+}
+
+impl From<Number> for String {
+    fn from(value: Number) -> Self {
+        let string_vec: Vec<String> = value
+            .digits
+            .iter()
+            .map(|&digit| digit.to_string())
+            .collect();
+        string_vec.concat()
+    }
+}
+
+impl From<&str> for Number {
+    fn from(value: &str) -> Self {
+        let bytes = value.as_bytes();
+        let (sign, idx_start) = match bytes[0] {
+            b'-' => (Sign::Negatif, 1),
+            _ => (Sign::Positif, 0),
+        };
+        let mut digits = vec![];
+        for &byte in &bytes[idx_start..] {
+            let digit = Self::byte_to_digit(byte);
+            digits.push(digit);
+        }
+        Self { digits, sign }
+    }
+}
+
+impl From<isize> for Number {
+    fn from(value: isize) -> Self {
+        let mut sign = Sign::Positif;
+        if value < 0 {
+            sign = Sign::Negatif;
+        }
+        let num_len = if value > 0 {
+            (value as f64 + 1.0).log10().ceil() as usize
+        } else {
+            1
+        };
+        let mut digits = vec![];
+        for digit_idx in 0..num_len {
+            let digit = Self::get_digit(value, digit_idx);
+            digits.push(digit);
+        }
+        let digits = digits.iter().rev().copied().collect();
+        Self { digits, sign }
+    }
+}
+
+impl Display for Number {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        let number_string = self
+            .digits
+            .iter()
+            .map(|&digit| digit.to_string())
+            .collect::<Vec<String>>()
+            .join("");
+        match self.sign {
+            Sign::Positif => write!(f, "{number_string}"),
+            Sign::Negatif => write!(f, "-{number_string}"),
+        }
+    }
+}
+
+impl Add for Number {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        let self_len = self.digits.len();
+        let rhs_len = rhs.digits.len();
+        let mut self_digits = self.digits.clone();
+        let mut rhs_digits = rhs.digits.clone();
+        if self_len != rhs_len {
+            let difference = (self_len).abs_diff(rhs_len);
+            let pad = vec![0isize; difference];
+            if min(self_len, rhs_len) == self_len {
+                self_digits = [pad, self.digits].concat();
+            } else {
+                rhs_digits = [pad, rhs.digits].concat();
+            }
+        }
+        let zipped = zip(self_digits.iter(), rhs_digits.iter());
+        let added = zipped
+            .map(|(self_digit, rhs_digit)| self_digit + rhs_digit)
+            .collect();
+        let mut overflown_number = Self {
+            digits: added,
+            sign: Sign::Positif,
+        };
+        overflown_number.handle_overflows();
+        overflown_number
+    }
+}
+
+impl Sub for Number {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        let self_len = self.digits.len();
+        let rhs_len = rhs.digits.len();
+        let mut self_digits = self.digits.clone();
+        let mut rhs_digits = rhs.digits.clone();
+        if self_len != rhs_len {
+            let difference = (self_len).abs_diff(rhs_len);
+            let pad = vec![0isize; difference];
+            if min(self_len, rhs_len) == self_len {
+                self_digits = [pad, self.digits].concat();
+            } else {
+                rhs_digits = [pad, rhs.digits].concat();
+            }
+        }
+        let zipped = zip(self_digits.iter(), rhs_digits.iter());
+        let added = zipped
+            .map(|(self_digit, rhs_digit)| self_digit - rhs_digit)
+            .collect();
+        let mut underflown_number = Self {
+            digits: added,
+            sign: Sign::Positif,
+        };
+        underflown_number.handle_underflows();
+        underflown_number
+    }
+}
+
+impl Mul for Number {
+    type Output = Self;
+
+    fn mul(self, rhs: Self) -> Self::Output {
+        let multiplied = self.digits.iter().rev().enumerate().map(|(pos, &digit)| {
+            let mut mult = digit * rhs.clone();
+            mult.digits = [mult.digits, vec![0; pos]].concat();
+            mult
+        });
+        let mut overflown_number = multiplied.reduce(|acc, num| acc + num).unwrap();
+        overflown_number.handle_overflows();
+        overflown_number
+    }
+}
+
+impl Mul<Number> for isize {
+    type Output = Number;
+
+    fn mul(self, rhs: Number) -> Self::Output {
+        let multiplied = rhs.digits.iter().map(|digit| digit * self).collect();
+        let mut overflown_number = Number {
+            digits: multiplied,
+            sign: Sign::Positif,
+        };
+        overflown_number.handle_overflows();
+        overflown_number
+    }
+}
+
+impl Mul<isize> for Number {
+    type Output = Self;
+
+    fn mul(self, rhs: isize) -> Self::Output {
+        let multiplied = self.digits.iter().map(|digit| digit * rhs).collect();
+        let mut overflown_number = Self {
+            digits: multiplied,
+            sign: Sign::Positif,
+        };
+        overflown_number.handle_overflows();
+        overflown_number
+    }
+}
+
+impl Div for Number {
+    type Output = Self;
+
+    fn div(self, rhs: Self) -> Self::Output {
+        Self::div_with_rem(self, rhs).0
+    }
+}
+
+impl Rem for Number {
+    type Output = Self;
+
+    fn rem(self, rhs: Self) -> Self::Output {
+        Self::div_with_rem(self, rhs).1
+    }
+}
+
+#[cfg(test)]
+mod number_tests {
+    use crate::number::{Number, Sign};
+
+    #[test]
+    fn test_from_isize() {
+        let number = Number::from(-1234);
+        assert_eq!(
+            number,
+            Number {
+                digits: vec![1234],
+                sign: Sign::Negatif
+            }
+        );
+    }
+
+    #[test]
+    fn test_get_digit() {
+        let num = 12345;
+        let digit_1 = Number::get_digit(num, 0);
+        let digit_2 = Number::get_digit(num, 1);
+        let digit_3 = Number::get_digit(num, 2);
+        let digit_4 = Number::get_digit(num, 3);
+        let digit_5 = Number::get_digit(num, 4);
+        assert_eq!(digit_1, 5);
+        assert_eq!(digit_2, 4);
+        assert_eq!(digit_3, 3);
+        assert_eq!(digit_4, 2);
+        assert_eq!(digit_5, 1);
+    }
+}
diff --git a/src/permutation.rs b/src/permutation.rs
new file mode 100644
index 0000000..98e911d
--- /dev/null
+++ b/src/permutation.rs
@@ -0,0 +1,83 @@
+use std::error::Error;
+
+fn factorial(num: usize) -> usize {
+    let mut fact = 1;
+    for n in 1..=num {
+        fact *= n;
+    }
+    fact
+}
+
+#[derive(Clone)]
+pub struct Permutator<T: Copy + Ord> {
+    pub current: Vec<T>,
+    idx: usize,
+}
+
+impl<T: Copy + Ord> Permutator<T> {
+    pub fn new(elements: Vec<T>) -> Self {
+        Self {
+            current: elements,
+            idx: 0,
+        }
+    }
+
+    /// Explanation
+    ///
+    /// there are 10! possible permutations
+    /// for each first number there are 9!, for each first 2 numbers 8!, etc.
+    /// we check how many times we have 9! permutations before we're over 1_000_000
+    /// aka. 1000000 / 9!
+    /// we take the remainder and check how many times we have 8! before we?re over it
+    /// (1000000 % 9!) 8!
+    /// etc.
+    /// every iteration we remove the digit by the idx from the original permutation
+    /// we only check for 999999 permutations because we already have the first one
+    ///
+    pub fn nth_lex(mut digits: Vec<T>, nth: usize) -> Result<Vec<T>, Box<dyn Error>> {
+        digits.sort();
+        if nth == 1 {
+            return Ok(digits);
+        }
+        if nth > factorial(digits.len()) || nth == 0 {
+            return Err(Box::from("Out of bounds"));
+        }
+        let mut perm = Vec::new();
+        let num_unique_digits = digits.len();
+        let mut remainder = nth - 1;
+        for idx in 1..=digits.len() {
+            let permutations = remainder / factorial(num_unique_digits - idx);
+            remainder %= factorial(num_unique_digits - idx);
+            perm.push(digits[permutations]);
+            digits.remove(permutations);
+        }
+        Ok(perm)
+    }
+}
+
+impl<T: Copy + Ord> Iterator for Permutator<T> {
+    type Item = Vec<T>;
+    /// Returns the next permutation and changes the current permutation to it
+    /// This operation wraps around
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current.is_empty() {
+            return None;
+        }
+        let mut digits = self.current.clone();
+        if self.idx == factorial(digits.len()) {
+            return None;
+        }
+        let mut perm = Vec::new();
+        let num_unique_digits = digits.len();
+        let mut remainder = 1;
+        for idx in 1..=digits.len() {
+            let permutations = remainder / factorial(num_unique_digits - idx);
+            remainder %= factorial(num_unique_digits - idx);
+            perm.push(digits[permutations]);
+            digits.remove(permutations);
+        }
+        self.idx += 1;
+        self.current = digits;
+        Some(self.current.clone())
+    }
+}