The duodecimal system (also known as base 12 or dozenal) is a positional notation numeral system using twelve as its base.
base 13
base 13 is a positional numeral system with thirteen as its base. It uses 13 different digits for representing numbers. The digits for base 13 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, and c.