The total supply of Bitcoin is 21 million coins.
So far, about 19.7 million have been mined, which means there are approximately 1.3 million Bitcoins left.
The last Bitcoin is expected to be mined in the year 2140 due to the Halving mechanism that reduces the reward every 4 years.
2. The reserves of countries or companies in Bitcoin?
Some countries, like El Salvador, have an official reserve of Bitcoin.
Companies like MicroStrategy own hundreds of thousands of Bitcoins as an investment.
3. The Bitcoin reserves on trading platforms?
There are periodic reports that outline the amount of Bitcoin available on trading platforms, and it is often lower over time due to increased cold storage by individuals and institutions.