haha, that is actually not technically correct

first of all is the fact that we can never mine all the 21 million coins because reward is halved so it will never actually reach zero. apparently it goes to zero after block 6930000. thanks BurtW

secondly is taking all the lost coins into consideration, a lot are burned by being sent to burn addresses, a lot are lost because someone forgot the private keys.

third if we ignore all the second step, there is 1 satoshi from missing from all the mining rewards thanks to a miner who intentionally got underpaid 1 satoshi less as an honor to satoshi missing. so even if all the coins are mined the total number will be 21 million minus 1 satoshi.