Originally Posted by

**Bacterius** May I use the computer to reply ? (Giggle)

*I have a marvellous proof for this problem which this textbox is too narrow to contain.*

Honestly, I don't know, there might be some mathematical trick that can be used here mentally, but I don't see how to do it without at least performing some operations of the same order of magnitude as the number. And the solution given in Wilmer's link is fallacious : how the hell are we supposed to *somehow* notice that $\displaystyle 2438100000001 = x^5 + x^4 + 1$ ? xD