Mysterious 6174!

Read this at wastedmonkeys:

Try this out!! Fascinating results!!

First choose a four digit number where the digits are not all the same (that is not 1111, 2222,...). Then rearrange the digits to get the largest and smallest numbers these digits can make. Finally, subtract the smallest number from the largest to get a new number, and carry on repeating the operation for each new number. You WILL get the mysterious number 6174 every time!!

For e.g., if we randomly choose say 1793.The maximum number we can make with these digits is 9731, and the minimum is 1379. Carrying out the subtractions:

9731 - 1379 = 8352
8532 - 2358 = 6174!!!!

Another eg, if we choose say 2951:

9521 - 1259 = 8262
8622 - 2268 = 6354
6543 - 3456 = 3087
8730 - 0378 = 8352
8532 - 2358 = 6174!!!!

If you continue the calculations on the number 6174, you'll repeatedly get 6174!!

This mysterious calculation called Kaprekar's Operation was devised by an Indian mathematician in 1949