import math


def isPrime(number):
    """Returns True if number is prime, otherwise returns False."""
    # Handle special cases:
    if number < 2:
        return False
    elif number == 2:
        return True

    # Try to evenly divide number by all numbers from 2 up to number's
    # square root.
    for i in range(2, int(math.sqrt(number)) + 1):
        if number % i == 0:
            return False
    return True