I'd be interested to see some data on how children learning math in Hindi do, because the numbers are even less regular, enough so that even though there's a pattern, you still have to learn all the numbers from 1-100 individually. There are also more specific words for different fractions, such as a word for 3/4 that sounds nothing like the word for 1/4.

http://www.sf.airnet.ne.jp/~ts/language/number/hindi.html

http://faculty.maxwell.syr.edu/jishnu/101/numbersfractions/d...

(My apologies if any of this is wrong. I'm not a native speaker, just took a few years of Hindi in college.)