If you can see another persons license then you can work out your own drivers' number; it's based on your initials, surname and date of birth. It uses three initials, if you only have two then the third slot is replaced by a 9, I think it uses 5 letters from your surname ( for names with less characters I'm not sure what the replacement character is, could be Z), the final field is based on your birth date (e.g. 1 March 1967 would be 601037, 27 May 1976 would be 727056)
So Frederick Joseph Bloggs born on 1st April 1963 would have a driver number something like 9FJ BLOGGS 601043