Hi,

I can vaguely remember that someone amazed me once that he could **calculate the 5th root of a natural number** that I had to write down for him. I just had to promise that the result is a regular integer as well, then he would stare at the number *for a couple of seconds* and then he told me the result. It was not a math genius or so, a normal student. I think the numbers I presented him were like 1027^5 and such.

What is the trick? I know of many tricks, how to check for dividability-by-three ans so on, but the 5th root?

thanks!

towi.