The total number of all Bitcoins that can ever be mined is exactly 21 million BTC. Right from the start, the supply of Bitcoin was made scarce in order to prevent Bitcoin from being issued in an inflationary manner. Currently, however, more than 90 percent of all possible Bitcoins have already been mined, in figures that is about 19 million BTC.
With each Bitcoin mining, the computational tasks to generate new Bitcoins become more difficult. Due to Bitcoin halving, it is inherent in the system that the fixed minimum number of Bitcoin cannot be exceeded. According to calculations, it will take around 120 years until all of the approximately 2 million Bitcoin that are theoretically still available have been mined.