Previews Example View All C Programs Next Example

# Program to Check Whether a Number is Prime or Not in C

A positive integer which is only divisible by 1 and iself is known as prime number. For example: 13 is a prime number because it is only divisible by 1 and 13 but, 15 is not prime number because it is divisible by 1, 3, 5 and 15.

#include <stdio.h> int main() { int n, i, flag=0; printf("Enter a positive integer: "); scanf("%d",&n); for(i=2;i<=n/2;++i) { if(n%i==0) { flag=1; break; } } if (flag==0) printf("%d is a prime number.",n); else printf("%d is not a prime number.",n); return 0; }

##### Result

Enter a positive integer: 29

29 is a prime number.

29 is a prime number.