题目：The prime factors of 13195 are 5, 7, 13 and 29.What is the largest prime factor of the number 600851475143 ?算法：#!/usr/bin/env python#coding=utf-8a = 600851475143b = 0Li = 3Lwhil

题目：The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.Find the sum of all the primes below two million.算法：#!/usr/bin/env python#coding=utf-8sum = 2def is_prime(num):i = 2