base 4 is a positional numeral system with four as its base. It uses 4 different digits for representing numbers. The digits for base 4 could be 0, 1, 2, and 3.

base 33 is a positional numeral system with thirty-three as its base. It uses 33 different digits for representing numbers. The digits for base 33 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, and w.