According to the analysis, in a strict sense, the total amount of BTC is not 21 million; just like Bitcoin will be mineless in 2040, the 21 million supply cap is only a rough statement. Nearly 99.9% of Bitcoin will be mined around 2040; however, it will not be considered that Bitcoin will really stop production until 2140, after the BTC network has experienced 34 block reward halvings. Since satoshi is the smallest unit of Bitcoin, after 33 rounds of halvings, the block reward that has been reduced to 1 Satoshi cannot be divided anymore; so at the block height of 6930000, the network will stop generating new coins. The total amount will reach 20999999.97690000. Of course, this is only a theoretical value. If some miners deliberately receive less bitcoin lost in block rewards, the final total may have to be reduced.