Check if number is prime number

I would just like to ask if this is a correct way of checking if number is prime or not? because I read that 0 and 1 are NOT a prime number.

int num1;

Console.WriteLine("Accept number:");
num1 = Convert.ToInt32(Console.ReadLine());
if (num1 == 0 || num1 == 1)
{
    Console.WriteLine(num1 + " is not prime number");
    Console.ReadLine();
}
else
{
    for (int a = 2; a <= num1 / 2; a++)
    {
        if (num1 % a == 0)
        {
            Console.WriteLine(num1 + " is not prime number");
            return;
        }

    }
    Console.WriteLine(num1 + " is a prime number");
    Console.ReadLine();
}