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

A Prime Number is a positive integer greater than 1 which is divisible by 1 and itself. In other words, Prime number is a whole number greater than whose factors are 1 and itself. Examples of first few prime numbers are 2, 3, 5, 7, 11, 13..

Note : Number 2 is first and only even prime number.

## Program

``````
#include<stdio.h>
#include<conio.h>

int main()
{
int number, i, flag=0;
clrscr();

// Inputs
printf("Enter integer number: ");
scanf("%d", &number);

// Checking for prime
for(i=2;i<=number/2; i++)
{
if(number%i==0)
{
flag = 1;
break;
}
}

// Taking decision
if(flag==0 && number>=2)
{
printf("%d is PRIME.", number);
}
else
{
printf("%d is NOT PRIME.", number);
}

getch();
return(0);
}
``````

Output of above program :

```Run 1:
-----------
Enter integer number: 13 ↲
13 is PRIME.

Run 2:
-----------
Enter integer number: 16 ↲
16 is NOT PRIME.

Run 3:
-----------
Enter integer number: 1 ↲
1 is NOT PRIME.

Run 4:
-----------
Enter integer number: 2 ↲
2 is PRIME.

Note: ↲ indicates enter is pressed.
```