Find a two digit number, perfect square, the second digit is one more than the first (beginning easy...).
What's that, no one ? why then ?
Well, let's try a 4 digit number... still none ? are you sure ?
Well, 6 digits then ... Solution
And now the pocket calculator is hot, 10 digits... Solution
12 digits, raa sh..., my calculator displays just 10 digits ... Solution