Bitcoin is a decentralized digital currency that operates independently of any government or bank. It was created in 2009 and is one of the most popular cryptocurrencies in the world.

The total number of Bitcoin in circulation is estimated to be around 18 million. This number is different from the total number of Bitcoin that can exist, which is capped at 21 million. This limit was set by the creator of Bitcoin, Satoshi Nakamoto, to ensure that the currency remains rare and valuable.

The number of Bitcoin in circulation is constantly changing as new Bitcoin is created and existing Bitcoin is lost. This means that the total number of Bitcoin in circulation is an estimate, and could be different from the actual number.

In addition to the 18 million Bitcoin in circulation, there are also a large number of Bitcoin that are currently being held by investors and not being used. This means that there is a potential for the total number of Bitcoin in circulation to increase significantly in the future.