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xkcd #2835: Factorial Numbers
(imgs.xkcd.com)
Alt text:
So what do we do when we get to base 10? Do we use A, B, C, etc? No: Numbers larger than about 3.6 million are simply illegal.
It begins to improve related to regular base-10 after, well, 10!, but it takes a while to recover for lower base numbers before that.