proof of the kaprekar constant if you enter any 4 digit number where the digits are not all the same (like 3333 or 6666) it will put the digits in descending order and then take away the digits in ascending order from that number. If you do this a few times it will always come to the number 6174 and then stay there. For example, take the number 6767: 7766-6677=1089 9810-189=9621 9621-1269=8352 8532-2358=6174 7641-1467=6174 7641-1467=6174 7641-1467=6174 7641-1467=6174 7641-1467=6174 .......
if you press space you can click the mouse to see each individual iteration, otherwise it will do that automatically.
