base 20 is a positional numeral system with twenty as its base. It uses 20 different digits for representing numbers. The digits for base 20 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, i, and j.

conversion table

base 20	base 17	base 20	base 17
1	≈ 1	b	≈ b
2	≈ 2	c	≈ c
3	≈ 3	d	≈ d
4	≈ 4	e	≈ e
5	≈ 5	f	≈ f
6	≈ 6	g	≈ g
7	≈ 7	h	≈ 10
8	≈ 8	i	≈ 11
9	≈ 9	j	≈ 12
a	≈ a	10	≈ 13