Base 64 to Base 39

Base 64

In base 64, each digit position represents a power of 64: the rightmost digit counts individual ones, the next counts groups of 64, the next counts groups of 64×64, and so on — the same place-value idea as base 10, just with 64 distinct digits instead of ten.

Base 39

Base 39 works the same way: the rightmost digit counts ones, the next counts groups of 39, the next counts groups of 39×39, and so on, using 39 distinct digits.