The default limit for atoms is 1,048,576 (see here). You could increase it by providing the +t n option, e.g. iex --erl "+t 20000000".
However, 10 million functions seem quite extreme, so not sure if you’ll bump into some other problems. Perhaps considering other options, such as multiclauses, or statically generated maps, or some such would work better. In any case, I’m curious to read more about your experiences with it.
