Speaking of fourdigit numbers and constant functions, here's a trick:
Take any four digit number whose digits aren't all the same (e.g., 7274), rearrange its four digits into order (e.g., 2477), and subtract this from its reverse (e.g., 7742  2477 = 5265).
Keep repeating this process till you get the same value twice in a row (so, in this example, 5265 then becomes 6552  2556 = 3996; this in turn becomes 9963  3699 = 6264; and one can continue in this fashion a couple more times before getting a repeat).
What value did you get at that point? It'll always be the same: 6174.
Last edited by Indistinguishable; 08262016 at 10:44 PM.
