# C++ Program to Check if a Number is Prime Number or not

## C++ Program to Check Whether the Number is Prime or Not

Prime number is a number which can be divided by 1 and itself i.e. a number which can not be divided by any other number other than 1 or itself is a prime number.

Example: 2,3,5,7,11….so on  are the prime number as we can see they only have two divisors, 1  and the number itself.  ## 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<iostream>
using namespace std;
main()
{
int i=1,num,div=0; //initializing variables
cout<<"Enter number:"; cin>>num; //user input
for(i=1;i<=num;i++) //checking for number of divisor
{
if(num%i==0)
{
div++;
}
}
if(div==2) //no divisors other than 1 and itself
{
cout<<num<<" is a prime number";
}
else
{
cout<<num<<" is not a prime number";
}
return 0;
}```

## Output

```Enter number:3
3 is a prime number
``` 