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

A number is considered as prime number when it satisfies the below conditions.

• Prime number is a number which can be divided by 1 and itself
• A number which can not be divided by any other number other than 1 or itself is a prime number.
• It should have only 2 factors. They are, 1 and the number itself.

## Problem Description

In this program we will find whether a number is a prime number or not with the help of for loop or if else statement. A number is considered as prime number when it satisfies the below conditions.

• Prime number is a number which can be divided by 1 and itself
• A number which can not be divided by any other number other than 1 or itself is a prime number.
• It should have only 2 factors. They are, 1 and the number itself.

Ex- Number is 13. it have only 2 factor

• It is divisible by 1.
• And it is divisible by itself

So it is a prime number. ## Algorithm:-

1. Take input number n
2.  Initialize i=1
3.  Initialize div=0
4.  we have to count all the divisor of number from 1 to n
5.  run a loop from i=1 to n
1. if n%i==0  (if n is divisible by i)
1. increment div, div++
2. increment i by 1 ,i++
6. check div, if div==2 display prime, else display not prime ## C Code

```#include<stdio.h>
int main()
{
//initializing variables
int c,number,div=0;

//user input
printf("Enter number: ");
scanf("%d",&number);

//checking for number of divisor
for(c=1;c<=number;c++)
{
if(number%c==0)
{
div++;
}
}
//no divisors other than 1 and itself
if(div==2)
{
//display
printf("%d is a prime number",number);
}
else
{
//display
printf("%d is not a prime number",number);
}
return 0;
}```

## Output

```Enter number: 2
2 is a prime number``` 