Base-7 (aka septenary) number system uses seven symbols to code information. Most commonly, these symbols are, 0, 1, 2, 3, 4, 5 and 6.
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.