I was working on 1 trillion dollars(market cap) divided by 1000, which is 1 billion holders.
Not even close. Just over 20M could claim to own $100 but realistically that's closer to 6M as well.
Discussion
I'm just talking on-chain, like has the keys for an actual Bitcoin address.
If you count Bitcoin banks like Coinbase, Robinhood, Binance, or the ETFs the number of Bitcoin "owners" goes up but they aren't meaningful on a network level.