Too late to edit my own post but mturmon is correct, my guess about the number of digits was incorrect. Even with a uniform distribution, it still takes 8.44 digits in base 32 and 7.04 digits in base 64, not counting checksum:

https://www.wolframalpha.com/input/?i=log+base+32+of+%28%285...

https://www.wolframalpha.com/input/?i=log+base+64+of+%28%285...