Check if input is a prime number

int prime_check(int num)
{
    //2 is the only even prime number
    if(num == 2)
        return 1;
    //if num is even and not 2, then it is not prime
    else if(num % 2 == 0)
        return 0;

    //check all odd numbers up to sqrt of num to see if they are factors
    for(int i = 3; i <= sqrt(num); i+=2)
    {
        if(num % i == 0)
            return 0;
    }
    return 1;
}