# C++ program to check prime number

Given an integer number, we have to check whether it is a primer number or not using C++ program.
[Last updated : February 28, 2023]

## Problem statement

Prime numbers are those numbers which are divisible by itself only. In this program, we will learn how to check whether a given number is prime or not?

## Checking prime number in C++

To check prime number, read an integer number and check whether it is Prime or Not, to check prime number we implemented a function isPrime() that will take integer number as argument and return 1 if it is primer else it return 0.

## Program to check prime number in C++

```#include <iostream>
using namespace std;

//function declaration
int isPrime(int n);

int main()
{
int num;

cout << "Enter an integer number: ";
cin >> num;

if (isPrime(num))
cout << num << " is a prime number" << endl;
else
cout << num << " is not a prime number" << endl;

return 0;
}

//function definition
int isPrime(int n)
{
int i;
int prime = 1;

for (i = 2; i < (n / 2); i++) {
if (n % i == 0) {
prime = 0;
break;
}
}
return prime;
}
```

### Output

```First run:
Enter an integer number: 120
120 is not a prime number

Second run:
Enter an integer number: 111
111 is not a prime number

Third run:
Enter an integer number: 97
97 is a prime number
```