Kaprekar’s Constant
Kaprekar’s Constant is 6174. Now lets have some fun with this number.
Follow this simple algorithm to see the magic of this number.
1. Pick a four digit number. Each digit should be unique; no repeating digits. ex. 4367
2. Order the digits from largest to smallest. This is your large value. ex. 7643
3. Order the digits from smallest to largest. This is your small value. ex. 3467
4. Subtract the small value from the large value. ex. 7643-3467=4176
5. Return to step two unless the result is 6174 ex. 7641-1467=6174
The process can take up to seven iterations and will always give a result of 6174.
Once 6174 is reached, the answer will always be 6174.
Why is this so? Plus magazine! has the detailed explanation.