Mahomes is wearing number 15. I thought he was picking from 4 and 7 because 5 was taken (Santos). I guess 1 in front of 5 is 15 so it worked. It was his high school basketball jersey number.
Anyway, I like the numbers 12 and 16 for QBs. 15 reminds me of Tebow, but that can easily be fixed by good play by Mahomes in the future.