Prime Factorization Calculator

            def largest_prime_factor(n: int) -> int:
    if n < 2:
        raise ValueError("n must be at least 2")
    largest = 1
    divisor = 2
    while divisor * divisor <= n:
        while n % divisor == 0:
            largest = divisor
            n //= divisor
        divisor = 3 if divisor == 2 else divisor + 2
    return max(largest, n)

assert largest_prime_factor(360) == 5
          

            #include <assert.h>
#include <stdint.h>

uint64_t largest_prime_factor(uint64_t n) {
    uint64_t largest = 1;
    for (uint64_t divisor = 2; divisor <= n / divisor;
         divisor = divisor == 2 ? 3 : divisor + 2) {
        while (n % divisor == 0) {
            largest = divisor;
            n /= divisor;
        }
    }
    return n > largest ? n : largest;
}

int main(void) { assert(largest_prime_factor(360) == 5); }
          

            #include <cassert>
#include <cstdint>
#include <algorithm>

std::uint64_t largest_prime_factor(std::uint64_t n) {
    std::uint64_t largest = 1;
    for (std::uint64_t divisor = 2; divisor <= n / divisor;
         divisor = divisor == 2 ? 3 : divisor + 2) {
        while (n % divisor == 0) {
            largest = divisor;
            n /= divisor;
        }
    }
    return std::max(largest, n);
}

int main() { assert(largest_prime_factor(360) == 5); }
          

x86-64 NASM · System V ABI · Linux · integer arguments in rdi, rsi and rdx

            ; uint64_t largest_prime_factor(uint64_t n)
global largest_prime_factor
section .text
largest_prime_factor:
    mov r8, rdi             ; remaining n
    mov r9, 1               ; largest factor
    mov rcx, 2              ; candidate divisor
.candidate:
    mov rax, r8
    xor edx, edx
    div rcx
    cmp rcx, rax            ; divisor > remaining/divisor?
    ja .finish
.divide:
    mov rax, r8
    xor edx, edx
    div rcx
    test rdx, rdx
    jnz .next
    mov r8, rax
    mov r9, rcx
    jmp .divide
.next:
    cmp rcx, 2
    jne .odd
    mov rcx, 3
    jmp .candidate
.odd:
    add rcx, 2
    jmp .candidate
.finish:
    mov rax, r9
    cmp r8, rax
    cmova rax, r8
    ret
          

            function result = largest_prime_factor(n)
    remaining = abs(round(n)); result = 1; divisor = 2;
    while divisor * divisor <= remaining
        while mod(remaining, divisor) == 0
            result = divisor; remaining = remaining / divisor;
        end
        if divisor == 2, divisor = 3; else, divisor = divisor + 2; end
    end
    result = max(result, remaining);
end
          

            ClearAll[mwCalculate];
mwCalculate[n_Integer] /; Abs[n] >= 2 := Max[First /@ FactorInteger[Abs[n]]];