判断一个数是否为质数

#include <stdio.h>

int main() {

    int num = 17;

    int isPrime = 1;

    for (int i = 2; i <= num / 2; i++) {

        if (num % i == 0) {

            isPrime = 0;

            break;

        }

    }

    if (isPrime == 1) {

        printf("%d is prime\n", num);

    } else {

        printf("%d is not prime\n", num);

    }

    return 0;

}