素数的判定

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h> 
#include <math.h> 
int Prime_(long Num)
{
if (Num < 2)
return 0;
long i;
long n;
n = sqrt(Num);
for (i = 2; i <= n; i++)
{
if ((Num % i) == 0)
return 0;
else
return 1;
}
;
}
int main()
{
   long n;
printf("input a number: ");
scanf("%d", &n);
if (Prime_(n) == 1)
{
printf("%d is a prime number.\n", n);
}

else
{
printf("%d is not a prime number.\n", n);
}
system("pause");
return 0;

}