I personally think that the entire crypto-community numbers in the low millions. The total market cap of all cryptocurrencies is around $300 billion. Assuming there are at least 5 million people investing in cryptocurrencies, then that works out around $60,000 invested per person. However, I would assume that on average each person has less than $10,000 invested, so we can assume that roughly 30 million people are invested in cryptocurrencies.