Find the sum of all the primes below two million

The sum of the primes below 10 is 2+3+5+7=17. Find the sum of all the primes below two million.


Source: ProjectEuler.net

C Implementation:

#include <stdio.h> int checkprime(unsigned long long int N) { if(N<=1) return 0; else if(N>=2 && N<=3) return 1; else if(N%2==0 || N%3==0) return 0; else { unsigned long long int i; for(i=5;i*i<=N;i+=6) { if(N%i==0 || N%(i+2)==0) return 0; } return 1; } } int main(void) { unsigned long long int n,sum; for(n=2;n<=2000000;n++) { if(checkprime(n)) sum+=n; } printf("%llu",sum); return 0; }