Base 58 to Base 39

Base 58

In base 58, each digit position represents a power of 58: the rightmost digit counts individual ones, the next counts groups of 58, the next counts groups of 58×58, and so on — the same place-value idea as base 10, just with 58 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.