There are finitely many bitcoins. It’s getting harder and harder to mine them. Are they basically the first 21 million prime numbers? something like all primes less than 2^29? Maybe 3 bits for some sort of checksum or identifier?
the mining is a problem. It takes a lot of electricity to verify a set of transactions and to thereby earn some additional mined bitcoin. I can’t see how this could ever scale up to where it could handle serious transaction volume. It would seem to be too inefficient.