It's 10 digits and 6 numbers per symbol.
I think the probability of guessing would be 166, which is 1/16777216
And dont forget that every bet also plays for 4 jackpots: daily, weekly, monthly and season.

So you can win a few months from now, and you'll have no idea that the money came from Ethex...
The jackpot payment simply lands in your ETH account, right?