The significant thing is that at each moment that the trader count is at a prime number, it only takes one more trader to tip it to a non-prime, whereas the same does not obtain with each non-prime, so in terms of gaming the system it is asymmetric.

I created a plot of the 'probability' of a number being prime for the first 50 numbers. Traders may find this useful.

You haven't specified that alts can't bet, would you so clarify? Or otherwise?

@JussiVilleHeiskanen I won't bet. I would really prefer it if alts did not bet but there is no enforcement mechanism I could do.

@LarsOsborne This is the problem with self-resolving markets. Other traders nearly always have better information than yourself.