Class & Object for Check Prime

#include<bits/stdc++.h>
using namespace std;

class prime
{
public:
    int num,countl=0;

    prime(int a)
    {
        num=a;
    }

    void checknumber()
    {
        int i;
        for(i=2;i<=sqrt(num);i++){
            if(num%i == 0)
                countl++;
            else
                countl = countl;
        }
    }

    void display()
    {
        if(countl==0){
            cout << "Number is prime" << endl;
        }
        else
            cout << "Number is not Prime" << endl;
    }
};

int main()
{
    cout << "Input a number to check it is prime or not: ";
    int n;
    cin >> n;
    prime obj(n);
    obj.checknumber();
    obj.display();
    return 0;
}