On SkyscraperCity, while I was on that forum, I can see some stats, like what are the biggest number of users on a time. I'll just give you an example:
Most users ever online was 27,103, November 8th, 2012 at 06:09 AM.
SkyscraperCity is very famous, though.
"What is the square root of 2? 1.4141592653589793238" Seriously, I thought it was that. Too round?