Any natural number greater than 1 that can only be divided by 1 is referred to as a prime number.

**eg**: 2,3,5,7,11 these are the few examples of prime numbers, that can be divided by either 1 or by itself.

## Example Program to find the Primer Number in C

#include <stdio.h> int main() { int n, i, isPrimeNumber = 0; printf("Enter a positive integer Number: "); scanf("%d", &n); // 0 and 1 are not prime numbers // change isPrimeNumber to 1 for non-prime number if (n == 0 || n == 1){ isPrimeNumber = 1; } for (i = 2; i <= n / 2; ++i) { // if n is divisible by i, then n is not prime // change isPrimeNumber to 1 for non-prime number if (n % i == 0) { isPrimeNumber = 1; break; } } // isPrimeNumber is 0 for prime numbers if (isPrimeNumber == 0) printf("%d is a prime number.", n); else printf("%d is not a prime number.", n); return 0; }

Check if 11 is a primer number.

Check if 9 is a primer number.