504731 - 4731st at Dartmouth. They opened it during exam week when everyone was in the library and nearly the entire school registered on one day.

lemmings.

I'm 601804, also from Penn. Does 6xxxxx denote school?

Some prefixes from my friends lists:

100k = Columbia 200k = Stanford 300k = Yale 500k = Dartmouth 600k = Penn 1000k = Brown

Cornell = 400k, MIT = 700k, NYU = 800k, BU = 900k, Princeton = 1100k, UC Berkley = 1200k, Tulane = 1300k, Georgetown = 1400k, UVA = 1500k, and then I got bored.

You can keep plugging away IDs into http://facebook.com/profile.php?id=[id]

May I ask how you know your join-order at your school?

I'm guessing that 600,000 represents penn, but I am just guessing based on the numbers and what others have written.