I’ve long wondered why we don’t count in base 11 or base 6. People will say ‘We have 10 fingers’, but that is rather my point: You don’t need a “10s” column until you reach ”11”. Imagine an early farmer counting sheep- he gets to 10, then on 11 puts a stone in the ‘hands full’ pile.
Likewise, you can count to 5 on your one hand, then use the other to record 6.”1,2,3,4,5, Onehand, Onehand-1, onehandy-2 etc” This would allow you to count to 35 on just 10 fingers (Fivehand-five), then ‘Stone’ (say) for Sixhand.
Of course over time these would be slurred and contracted (like four-ten is 40): twoston threehandy four is nine-tens four.
Feel free to steal this for alien cultures in your RPGs!