Prime proc

#include <stdio.h>
#include <cmath>
int prime(int a){
	a = abs(a);
	if (a == 1 || a == 0) return false;
	int divider = 2;
	while(divider <= (a / 2 + 1) && divider != a){
		if (a % divider == 0) return false;
		divider++;
	} 
	return true;
}
int main(void) {
    int a = -7;
    printf("Num %d %s\n", a,prime(a) ? "is prime": "is not prime");
    return 0;
}