Question

How many whole numbers are there, whose squares and cubes have the same number of digits?

Answer 1

There are the following numbers for which that holds:

{-4, -2, -1, 0, 1, 2, 4}

See table below. For larger than 5 it can be proved that the number of digits will never be the same.

x   x^2  x^3

0 0 0

1 1 1

2  4  8

4  16  64