This simple isprime(number) function checks if the given integer number is a prime number and returns True or False. The function makes sure that the number is a positive integer, and that 1 is not considered a prime number.
To find out if an integer n is odd one can use
n & 1, to check for even one can then use
not n & 1 or the more traditional
n % 2 == 0 which is about 30% slower.