第三解：
The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?
解：
```python feed = 600851475143 def GetFactor(feed,footmark): while footmark < feed: footmark += 2 if feed % footmark == 0: print footmark GetFactor(feed / footmark,footmark) break GetFactor(feed,1) ```
