Milo;367893 wroteAll 9 quintillion of them . . .
Actually its lower than that, since the NCAA tournament went to the 64 teams, no 1 seed has ever lost to a 16 seed. Given that trend, it drops to 1 in 562,000,000 to pick the rest.
The sad part is, since offering bracket contests, CBS Sports and ESPN have never had anyone submit a perfect bracket. It is somewhere close to 50 million entries in total.