Hehe, to me these contrarian comments are strongly reinforcing my point about overzealous pedantry. :) Of course the specific string '6174' is specific to base 10, but the idea itself can be applied to other bases.

Here are some additional examples:

  dec, 3 digits: 495
  hex, 3 digits: 7F8
  hex, 30 digits: EECCAA88664421FFDDBB9977553312
  dec, 30 digits: 988766544332209987766554332111
  hex, 100 digits: FFFFEEEEDDCCCCBBAAAA9998888776666554444333222210FFFFEEDDDDCCCBBBBAA999988777766655554433332211110001
  dec, 100 digits: 9999998888888877666666665544444444332222222210999999998877777777665555555544333333332211111111000001

Whether or not things settle on a single number, the number of loops that exist, etc. are a function of the base and the number of desired digits, but in the cases where inputs do settle on a specific number, there are patterns that emerge (regardless of the base) as the number of digits go up.