How many possible Grainger part numbers?

[opmal7]

If anyone is not familiar with Grainger, they are an industrial supply company that sells just about everything you can imagine. I've always been particularly impressed by the fact that even though they carry so many parts, their part numbers are all 5 digits. I believe the first digit is always a number, and the next 4 digits are any combination of numbers and letters.

I'd like to see the math showing how many possible part numbers Grainger can have with this system.

 

[mathman]

10x36x36x36x36=16796160.