Summation of primes: program to print sum of all prime numbers upto 2000000

/*Program to print sum of all prime numbers upto 2000000*/

/*To check whether a number is prime or not it takes n^2 time by
  brute force but this program is sqrt(n) according to
  mathematical rules to check prime number efficiently.
*/

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#define MAX 2000000
int main()
{
  int i,j;
  unsigned long int prod=0;
  int prime;
  for(i=2;i<=MAX;i++){
    prime=1;
    for(j=2;j<(int)(sqrt(i)+1);j++){
      if(i%j==0){
        prime=0;
        break;
      }
    }
    if(prime==1){
      prod=prod+i;
    }
  }
  printf("%ld",prod);
  return 0;
}