base 11 is a positional numeral system with eleven as its base. It uses 11 different digits for representing numbers. The digits for base 11 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and a.

base 19 is a positional numeral system with nineteen as its base. It uses 19 different digits for representing numbers. The digits for base 19 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, and i.