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 36 is a positional numeral system with thirty-six as its base. It uses 36 different digits for representing numbers. The digits for base 36 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, and z.