prime number c++

#include <iostream>
#include <cmath>

using namespace std;

bool isPrime(int num);

int main() {
    int number;

    cout << "Enter a positive integer: ";
    cin >> number;

    if (isPrime(number))
        cout << number << " is a prime number." << endl;
    else
        cout << number << " is not a prime number." << endl;

    return 0;
}

bool isPrime(int num) {
    if (num <= 1)
        return false;

    for (int i = 2; i <= sqrt(num); ++i) {
        if (num % i == 0)
            return false;
    }

    return true;
}