It's so funny no one answered this, because a bunch of us have been here FOREVER! Your Mibba # is 115945 - if you click your username and look at your profile link, that's the number (: It stays the same even when Mibba changes so in the future if, say, profile links become #.mibba.com yours would be 115945.mibba.com! This helps identify you even after you change your username, too (:
I'm pretty lame - eternal bad luck - but I am loving Mibba, as always~