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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]

Checking prime number in C++

In this program, we will learn how to check whether a given number is prime or not?

Prime numbers are those numbers which are divisible by itself only. Here, we will 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

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