import math


def is_prime(number):
    """Determines if a single number is prime or not.
    """
    if(number <= 1):
        return False

    if(number == 2):
        return True

    a = int(math.sqrt(number))+1
    divisor = 3

    if((number % 2) == 0):
        return False

    while(divisor < a):
        if((number % divisor) == 0):
            return False
        divisor += 2
    return True