A rhetorical question, obviously. But check out this gentleman, who can calculate the 13th root of a 200-digit random number in his head, in just a little over a minute: http://www.smh.com.au/news/world/mathlete-works-out-200digit-number-in-head/2007/12/12/1197135500016.html.
Amazing! Not really all that useful, perhaps, but still amazing. . .
Best,
--- Les
[http://www.lesbell.com.au]