bool isEven(int number) {
  if (number % 2) {
    return true;
  } else {
    return false;
  }
}

#include <stdio.h>
#include <stdbool.h>

int main(void) {
  unsigned long num;
  unsigned long div;
  bool isPrime = true;

  num = 64457;

  for (div = 2; (div * div) <= num; div++) {
   if (num % div == 0) isPrime = false;
  }

  if (isPrime) {
    printf("%lu is prime.\n", num);
  } else {
    printf("%lu is not prime.\n", num);
  }

  return 0;
}