import math

largestPrimeFactor = 1
toBeFactored = 600851475143

def is_prime(maybeprime):
    for i in range(2, math.floor(math.sqrt(maybeprime) + 1)):
        if maybeprime % i == 0:
            return False
    return True

for i in range(2, math.floor(math.sqrt(toBeFactored) + 1)):
    if is_prime(i) and toBeFactored % i == 0:
        largestPrimeFactor = i

print("The largest prime factor of " + str(toBeFactored) + " is: " + str(largestPrimeFactor))