[leot]

The only way in which it makes sense to talk about numbers being written "right to left" or "left to right" is when comparing the order of speech sounds to the ordering of numerals read. In English it goes from the biggest to the smallest: "420" ==> "four hundred and twenty".

[rmk2]

Then German and Danish are neither left-to-right nor right-to-left, since 123 is einhundertdreiundzwanzig or hundredetreogtyve ("onehundredthreeandtwenty"), so that doesn't seem to work too well, either...