Write a program that tests whether an integer is a prime number.

#include <iostream>

using namespace std;

int main() {

   int n;

   cin>>n;//taking input form the user.

   bool b=true;

   for(int i=2;i<n;i++)//looping

   {

       if(n%i==0)//checking that i divides n.

       {

           cout<<"The number is not prime";

           b=0;

           break;

       }

   }

   if(b)

   {

       cout<<"The number is prime";

   }

return 0;

}

Input:-

23

Output:-

The number is prime.

Explanation:

The above written program is in C++.First I have declared an integer n.Then taking input form the user and storing it in n abd also declared a boolean variable with value true.Then I have used a for loop for checking n is divisible by any number from 2 to n-1 if it is then printing the message of not prime,making the value of b to false and coming out of the loop.out of the loop if the value of the b is true then printing the number is prime.