Well, you could just use the first few primes multiplied together as a base. 2 * 3 gives you base6, 2 * 3 * 5 gives you base30. Neither commonly used system does that, base12 uses 2 twice, base10 skips 3. So from a divisibility PoV both are lacking. But arithmetics is base10 anyways, since thats close to the average number of fingers for humans, so...