Numbers are a funny thing, they our anchor in language. Perhaps it is because you can speak a number in any language. You might be in China and of course you cannot speak chinese, but you see something you want to buy. The sales lady says something in Chinese and you want three pieces. The wonder of sign language: you point and show three fingers, and everyone understands.
I speak many languages, none perfect. When speaking german I think in german, but if I have to count, solve a mathematical problem, I do it in English. I once had a Pakistani boss who spoke perfect english, but if he had to calculate he would do it in Urdo and really sounded strange. I speak Italian, speak Russian, speak French, no exactly perfect, but can count in those languages, know the numbers, but if I have to do my own arithmetic, on the market when buying goods, or just for my own purpose, I do it in English. I am sure there are many of you here from various countries, but we all use english here basically as our common language, but if you have to count I would bet that you all count in your mother tongue.
I am sure that Sigmund Freud or Carl Jung or any other psychiatrist could say why. The brain is a calculator, but only in its own language.