How to manipulate large numbers in C? -

i wrote algorithm check if number prime , numbers divide it. want know 600851475143 divisors (for example) , outputs negative number. that's code:

#include <stdio.h> /* discover numbers divide 1 read input, show if it's prime */  int main() {     long checker;     long step = 1;     int divisors = 0;      printf("enter number want know divisors: ");     scanf("%d", &checker);     while(step <= checker){         /* check numbers divide number read*/         if (checker % step == 0) {             printf("%d divides %d\n", step, checker);             step +=1;             divisors +=1;              }             else{                 step+=1;                 }     }      /*now check if prime*/     if (divisors == 2) {         printf("additional info: %d prime number.\n", checker);     }     else {          printf("additional info: %d not prime number.\n", checker);     }     printf("done!\n");      return 0; } 

the problem scanf long using format string %d expects address of int variable. same goes way use printf.

you need replace every %d %ld in format strings. need because size of int , of long not equal.

edit: gcc points out mistake using -wall option.