The odds of drawing a royal flush are 30,939 to 1. The chances of pulling 20 out of 20 on an 80-ball Keno are about 3.5 quintillion to 1. Hitting a single number on roulette carries a probability of 35 to 1 against. Gamblers love to know the odds. It is the intriguing part of the strategy. Even when looking at the business of gambling, we all become Jimmy the Greek and look at the spread.