To be honest, I wouldn't have a clue how to find it on any other mobile phone either (and googling suggests that there isn't a standard or common way of doing it).
AFAIK, the number is not stored on the SIM.
The operator maintains a mapping table which links the SIM serial number to the phone number: this way, if you lose the SIM or switch operator, all it takes is editing that table.
I believe there is no option for checking your sim card numbers , you can just see it when copied from the sim card in the contacts app. You can't also save a number to sim card , which is annoying . There is a bug in the contacts app and nokia should fix it as soon as possible.
It just reminds me of iPhone copy and paste issue (lol). Still I don't really understand how can you see your number on let's say, Nokia n95 while there's a problem with n900.
