using System;

public class Program

{

    public static void Main()

    {

        int number = 7; // Change this to the number you want to check

        bool isPrime = IsPrime(number);

​

        if (isPrime)

        {

            Console.WriteLine(number + " is a prime number.");

        }

        else

        {

            Console.WriteLine(number + " is not a prime number.");

        }

    }

​

    static bool IsPrime(int num)

    {

        if (num <= 1) return false;

        if (num == 2) return true; // 2 is the only even prime number

        if (num % 2 == 0) return false; // Other even numbers are not primes

​

        for (int i = 3; i <= Math.Sqrt(num); i += 2)

        {

            if (num % i == 0) return false;

        }

​

        return true;

    }

}