[meitham]

It actually used to be right to left, just like the language! In some formal communication it's still the case, like when news channel announce new year "one and eighty and nine hundreds and a thousand. The change to read from left to right started fairly recently in the twentieth century, along with the change of the order of alphabets from أبجدهوز to أبتثجحخ.

I'm a native Arabic speaker, and yes I still struggle to both: speak P and hear P, Put no BroPlem!

[phicoh]

I'm curious, when was it right to left?

In computer speak, the way we write numbers in English is 'big endian'. We write the most significant digit first.

The most common 'little endian' system is postal addresses, where we start with the smallest unit (name) then in, some cases, house number, street, city, country.

Note that roman numerals are commonly written in big ending way. So this practice is very old.

[NeedMoreTea]

Yet historically English numbers were little endian, base twenty: "four and twenty" etc. Base 20 comes from Celtic roots I think, so perhaps other European languages have a similar history too.