Interesting mathematical trivia I learnt from my daughter yesterday about a special number called Kaprekar’s constant.
Take any 4 digit number with at least two distinct digits. Make the biggest and the smallest number out of these digits and find the difference between the two. Repeat the same process with the new number i.e. the difference that you just found. In a maximum of 7 iterations you will reach the number 6174, the Kaprekar’s constant!
There is a similar constant for 3 digits which is 495.
read more about it at http://en.wikipedia.org/wiki/6174