# ch9/example1.py

from math import sqrt

def is_prime(x):
    print('Processing %i...' % x)

    if x < 2:
        print('%i is not a prime number.' % x)

    elif x == 2:
        print('%i is a prime number.' % x)

    elif x % 2 == 0:
        print('%i is not a prime number.' % x)

    else:
        limit = int(sqrt(x)) + 1
        for i in range(3, limit, 2):
            if x % i == 0:
                print('%i is not a prime number.' % x)
                return

        print('%i is a prime number.' % x)

if __name__ == '__main__':

    is_prime(9637529763296797)
    is_prime(427920331)
    is_prime(157)