base 28 is a positional numeral system with twenty-eight as its base. It uses 28 different digits for representing numbers. The digits for base 28 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, and r.

base 25 is a positional numeral system with twenty-five as its base. It uses 25 different digits for representing numbers. The digits for base 25 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, and o.