Roughly 26,700,000,000,000,000,000,000,000 google tells me. That's more than play the clash!
Edit: Seriously though it's not even on Nico's bug log. I don't want to risk the wrath of Champ by speculating on whether the things on the log or those missing are likely to be fixed but I think (that's I think...not they are) wgt are happy with the current numbers in the Showdown. As Mio indicated even if some on the forum joined you, say 20 which would be a lot, it wouldn't make a difference.
I had my share of this in the 100c one and just play for 10c now, with the added bonus that even if you're hit with this in the first two rounds it needn't mean you don't qualify.