Problem 3 Largest prime factor

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

import mathdef is_prime(n):        if n < 2:return False        for i in range(2,int(math.sqrt(n))+1,1):                if not n % i :return False        return Truedef run(n):        for i in range(3,int(math.sqrt(n))+1,2):                if not is_prime(i):continue                if n == i:return n                if not n % i: n = n / iprint run(13195)print run(600851475143)