In decimal representation find the largest N-digit number which is an N-th power.
(In reply to Solution (Spoiler)
I interpreted the puzzle differently from broll. I thought the request was to find the generalized answer for various N, such as 81 is the largest 2-digit number that's a perfect square (16, 25, 36, 49, 64 being others); 729 is the largest 3-digit cube (125, 216, etc. being others), etc. So I thought:
9^N will work up through N=21. Beyond that there does not exist an N-digit number that's a perfect Nth power.
9^21 is the 21-digit number 109418989131512359209, while 9^22 is also a 21-digit number: 984770902183611232881. It's all downhill from there.
Posted by Charlie
on 2015-06-24 09:48:19