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-3 (also called ternary or trinary) number system uses three symbols to code information. Most commonly, these symbols are, 0, 1 and 2.