I think that is partly why LLMs are bad at math and often fail at counting subsequences. Play with the tokenizer and you see long numbers are split into groups of 2 or 3 numbers.

https://huggingface.co/spaces/Xenova/the-tokenizer-playgroun...

Imagine designing and building an aqueduct with Roman numerals.

You use a counting board rather than paper: https://www.youtube.com/watch?v=UVB27kKAcRs&t=111

The main advantage of Arabic numerals on paper have is that operations are non destructive and you can restarts a calculation if you lose your place. The main disadvantage is memorising the times table and the amount of scratch paper you need.