Why 21 Million Bitcoin?

Why exactly 21 million? Why not 20, 25 or even 100 million? How does this number come about?

Well, this is a question that divides opinions, because Satoshi Nakamoto himself has never given a clear answer to this question. Some people think that the amount of Bitcoin was chosen so that if the entire world's money supply was represented in Bitcoin, 1 cent would be about 1 Satoshi. However, most people simply believe in some arbitrariness that comes with the fact that Satoshi wanted to set the average block time at 10 minutes and the so-called block subsidy was supposed to halve every 4 years or so.

Coupled with an (equally arbitrarily set?) initial reward of 50 BTC per new block, you just end up with the 21 million BTC as the limit.

Let's do some math ????

6 blocks per hour x 24 hours per day x 365 days x 4 years = 210,240 blocks per cycle.

However, since Nakamoto didn't want to choose such a "crooked" number for the cycle he rounded down to 210,000 blocks (that's the theory).

The sum of all block subsidies adds up to infinity: 50 + 25 +12.5 + 6.25 +3.125 + .... = 100.

So, in theory, we actually arrive at :

210,000 blocks x 100 BTC = 21,000,000 BTC.

However, there is one problem. And that is the Bitcoin protocol itself. In it, only eight decimal places are defined for Bitcoin.If halving the block subsidy results in the new subsidy having more than these eight decimal places, then, according to the Bitcoin source code, everything from the ninth place is simply truncated.

If you calculate it to the end Bitcoin already reaches its maximum limit at 20,999,999.97690000 BTC. So there will never be 21 million Bitcoin. But it will be close