Here's something you might not know: College basketball players can't wear uniforms that have the digits 6 through 9. And it's for a pretty weird reason.
When a referee calls a foul, he throws up the offending player's numbers with his fingers.
You might see the problem. Most refs have only five fingers on each hand. So, no digits above 5.
Seriously, it's right there in the NCAA rulebook. A rule lists all the numbers teams can use, and none of them have a digit above 5. That means 55 is the highest number you can put on a jersey.
If it seems like they should be able to get around this, you're probably right. In the NBA, players can wear whatever number they want. Officials use both hands for larger digits.
But that signal might be confused for a 51. Right now, that's a risk the NCAA isn't willing to take.