Comment by aragonite

In my observation of non-native speakers working & living in the US (a group to which I belong), there's also something special about number-words. If you are a non-native speaker, even if you boast near-perfect English pronunciation and fluency, and are accustomed to using English in all aspects of your life, not just for communication but for e.g. personal note-taking, and even if you haven't spoken/written your native language with anyone in months, the moment you need to count (a sizable enough collection), or you need to enter on your computer a numerical passcode received on your smartphone, you (most likely) find yourself reverting (in your (sub)vocaliztion) to the number-words of your mother tongue, because doing the same thing in English just feels so much more cumbersome.