Indian Mathematicians

I came across an article that outlines the contributions made to mathematics by Indian mathematicians. One of the things that caught my attention was a contribution by a mathematician called Kaprekar.

"Kaprekar Constant" is 6174 and works as follows:

Take any four digit number in which all digits are not alike. Arrange its digits in descending order and subtract from it the number formed by arranging the digits in ascending order. If this process is repeated with reminders, ultimately number 6174 is obtained, which then generates itself.