Base-20 (also known as vigesimal) number system uses 20 symbols to code information. Most commonly, these symbols are, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 'A to J' (or alternatively 'a to j').
Base-6 (also called senary or heximal or seximal) number system uses six symbols to code information. Most commonly, these symbols are, 0, 1, 2, 3, 4 and 5.