base 15 is a positional numeral system with fifteen as its base. It uses 15 different digits for representing numbers. The digits for base 15 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, and e.

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.