I've succesfully written some code that prints out the prime factors of integers. It works succesfully for small-ish integers, but my task is to calculate the largest prime factors of 600851475143. Here is my code, which works for the number 13195.

Simply replacing the '13195' on line 10 with the huge integer 600851475143 doesn't work, as C doesn't like integers that big. I did a bit of research on how to represent numbers that large. I tried to represent it as a constant of type 'double' using:Code:#include <stdio.h> int isprime (int n); int main() { int prime; int i; for (prime = 5; prime < 75; prime ++){ if (isprime(prime)&&13195%prime==0){ printf("A prime factor is %d.\n", prime); } } getchar(); return 0; } int isprime (int n) { int i; int boolean = 1; for (i = 2; i < n/2; i++){ if (n%i==0){ boolean = 0; } } return boolean; }

but that didn't work because of type differences, and it also failed when I typecasted f as an integer (it produced a large negative integer).Code:#include <cmath> double f = 6.00851475143*pow(10.0,11.0);

So is there any way to represent this huge integer that works, or must I find another method to work out the largest prime factor? I certainly can't think of another method