Base 16

In base 16, each digit position represents a power of 16: the rightmost digit counts individual ones, the next counts groups of 16, the next counts groups of 16×16, and so on — the same place-value idea as base 10, just with 16 distinct digits instead of ten.

Base 13

Base 13 works the same way: the rightmost digit counts ones, the next counts groups of 13, the next counts groups of 13×13, and so on, using 13 distinct digits.