Programming question

#1

Add all prime number less than 2 milion

#2 
#include <stdio.h>

unsigned isPrime(unsigned n);

unsigned sum = 0;

int main() {
  for (long i = 1; i < 2000000; i++) {
    if (isPrime(i)) {
      printf("%d ", i);
      sum += i;
    }
  }

  printf("Sum: %d", sum);
}

unsigned isPrime(unsigned n) {
  if (n <= 1)
    return 0;

  for (int j = 2; j <= sqrt(n); j++) {
    if ((n % j) == 0)
      return 0;
  }

  return 1;
}