To you math people!

[Mitica100]

Here is a gem:

Take a four digit number (this works best if the digits are all different) such as 3967.

Now, rearrange the digits from the highest to the lowest...

9763

Subtract from this the reverse:

9763-
3679
-------
5084

Repeat the same operation, rearranging the digits from the highest to the lowest and subtract the reverse from it:

8540-
0458
-------
7082

Do this as many times as you can, the end result will invariably be 6174. When you get to this number and do the same operation it gets you the same number, 6174:

7641-
1467
-------
6174

Any explanation to this magic number?

 

[nvr2low]

not sure, but im sure there is a proof for it somewhere

 

[mentos_007]

Kaprekar's constant ???