calculator

bool is_prime(int number) {
    if (number < 2) return false;
    if (number == 2) return true;
    if (number % 2 == 0) return false;
    for (int i = 3; (i * i) <= number; i += 2){
        if (number % i == 0 ) return false;
    }
    return true;
}