Prime number in C: **Prime number** is a number that is greater than 1 and divided by 1 or itself. In other words, prime numbers can’t be divided by other numbers than itself or 1. For example 2, 3, 5, 7, 11, 13, 17, 19, 23…. are the prime numbers.

#### Note: Zero (0) and 1 are not considered as prime numbers. Two (2) is the only one even prime number because all the numbers can be divided by 2.

Let’s see the prime number program in C. In this c program, we will take an input from the user and check whether the number is prime or not.

- #include<stdio.h>
- #include<conio.h>
- void main()
- {
- int n,i,m=0,flag=0;
- clrscr();
- printf(“Enter the number to check prime:”);
- scanf(“%d”,&n);
- m=n/2;
- for(i=2;i<=m;i++)
- {
- if(n%i==0)
- {
- printf(“Number is not prime”);
- flag=1;
- break;
- }
- }
- if(flag==0)
- printf(“Number is prime”);
- getch();
- }

Output:

Enter the number to check prime:56 Number is not prime

Enter the number to check prime:23 Number is prime