Base-4 (aka quaternary) number system uses four symbols to code information. Most commonly, these symbols are, 0, 1, 2 and 3.
Base-36 number system uses 36 symbols to code information. Most commonly, these symbols are, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 'A to Z' (or alternatively 'a to z').