Project Euler - Problem 3

problem3.c

#include <cs50.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

/*  
    Largest Prime Factor

    The prime factors of 13195 are 5, 7, 13 and 29.

    What is the largest prime factor of the number 600851475143 ?
*/

int largest_factor = 0;

void largestprime(long long n);

int main(void)
{
    long long number = 600851475143;
    largestprime(number);
    printf("The largest prime factor of %lli is %i\n", number, largest_factor);
}

void largestprime(long long n)
{
    int d = 2; //start checking primes at 2
    
    while (n > 1)
    {
        while (n % d == 0)
        {
            largest_factor = d;
            n /= d;
        }
        
        d++;
        
        if (d * d > n)
        {
            if (n > 1)
            {
                largest_factor = n;
                break;
            }
        }
    }
}