**The prime number program in C** is one of the most important programs in c.

**What is a prime number?**

Any number which is divisible only by one and itself. two (2) is the smallest even prime number. for example prime numbers are: 2, 3, 5, 7, 11, 13, 17,…..

A number is greater than one can be factorized into prime numbers, for example, 540 = 22*33*51.

## Algorithm for Prime number program in C

- Take the input number. no
- Set c=2
- Write loop for ( c = 2 ; c <= n – 1 ; c++ )

if n%c == 0

Print No is not a prime number

break; - If c == n

Print No is a prime number

## C Program to Check Whether a Number is Prime or not

#include<stdio.h> main() { int n, c = 2; printf("Enter a number to check if it is prime\n"); scanf("%d",&n); for ( c = 2 ; c <= n - 1 ; c++ ) { if ( n%c == 0 ) { printf("%d isn't prime.\n", n); break; } } if ( c == n ) printf("%d is prime.\n", n); return 0; }

**Output :**