Not to even mention danish numbers. They use a 20-base system from 50 up, but then they add some weird archaic expressions for 2.5, 3.5 and 4.5, which, along with truncation, makes the whole thing completely incomprehensible, even to someone who otherwise understands the language perfectly well.
Danish numbers
I remember going on vacation to denmark as a kid, and never managing to pay for something if it cost more than 50 (which is where the base 20 system kicks in).
"that will be seven-and-half-fifth-t."
"um, what?"
"seven. and. half. fiftht."
"um. right. here's money. i think there's quite a lot of it. could you just take what you need?"