21 isn't a key code for anything. Lookup "javascript keycode" on google to get a list of keycodes for the different key. Like this one:
http://www.javascripter.net/faq/keycodes.htm
Numpad 1's key code looks to be 97 if numlock is on.
Ooops... now I know, but is it possible to combine two Numpad keys? If i press 21 = audio is played. Is it possible? tnx..