Number 13  Universally the Unluckiest Number\n\n Said to refer to Judas, who was the 13^th disciple and who betrayed Jesus at the Last Supper, number 13 is perhaps one of the least played numbers in any form of betting.

So the probability of getting a red on any single spin is 18/37 or 18/38. The probability of getting 13 in a row is (18/37)^13 or (18/38)^13, or 1:11697 or 1:16544 respectively.