base 31 is a positional numeral system with thirty-one as its base. It uses 31 different digits for representing numbers. The digits for base 31 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, and u.

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.