base 12 is a positional numeral system with twelve as its base. It uses 12 different digits for representing numbers. The digits for base 12 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, and b.

base 17 is a positional numeral system with seventeen as its base. It uses 17 different digits for representing numbers. The digits for base 17 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, and g.