I just make one up.
Scru em.
I have numerous gmail accounts and they always ask for a number and I never give them a correct one. I don’t think it has any bearing, at least for me.
Google + accounts are another matter. But there are ways around that nonsense of “proving you are REAL” garbage also.
I like the idea of using numbers like the White House, etc. Think I will steal that one. And...ooo!...NSA would be a good one!
I am not a fan of ‘puter fascism: google doesn’t own the web...I do not particularly care what they want.