A Kaprekar number is an -digitpositive integer such that squaring
it and adding the right digits to the remaining left part (taken as 0 when empty)
gives . For example, 9 is a Kaprekar number since
and 297 is a Kaprekar number since
The first few are 1, 9, 45, 55, 99, 297, 703, ... (OEIS A006886).
-digit positive integer 
such that squaring
it and adding the right 
digits to the remaining left part (taken as 0 when empty)
gives 
. For example, 9 is a Kaprekar number since
