Kaprekar's constant: 6174

I just discovered Kaprekar's constant, 6174, named after an Indian mathematician. As noted in the Wikipedia article on the constant, "This number is notable for the following property:

1. Take any four-digit number with at least two digits different. (Leading zeros are allowed.)
2. Arrange the digits in ascending and then in descending order to get two four-digit numbers, adding leading zeros if necessary.
3. Subtract the smaller number from the bigger number.
4. Go back to step 2.

The above operation, known as Kaprekar's operation, will always reach 6174 in at most 7 steps and it stops there. Once 6174 is reached, the process will keep yielding 7641 – 1467 = 6174."

Weird.

I am pleased to discover the Wikipedia has entries on many individual integers.

The image comes from Plus Magazine, a magazine of mathematics- click the image for a more detailed article on 6174.