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Write a program in C++ to check whether a number is prime or not. 
Sample Output:
Input a number to check prime or not: 13
The entered number is a prime number.


#include <iostream>
using namespace std;
int main()
{
    int num1, ctr = 0;
    cout << " Check whether a number is prime or not: ";
    cout << "-------------------------------------------- ";
    cout << " Input a number to check prime or not: ";
    cin>> num1;    
    for (int a = 1; a <= num1; a++) 
    {
        if (num1 % a == 0) 
        {
            ctr++;
        }
    }
    if (ctr == 2) 
    {
        cout << " The entered number is a prime number. ";
    }
    else {
        cout << " The number you entered is not a prime number. ";
    }
}