Is your feature request related to a problem? Please describe.

• The Kaprekar Numbers algorithm that we have uses long, but in place of that BigInteger can be used.
• A function which will give a list of targeted numbers in a range.
  Describe the solution you'd like
• well, we need to change into BigInteger and add a simple function

Describe alternatives you've considered
well no alternatives planned

Additional context
The review to the PR.