About block 21
Bitcoin block 21 was mined by Unknown on January 10, 2009 at 5:49 AM UTC, 9 min 18 s after block 20. That is faster than the 10-minute average the network aims for: blocks come in bursts because finding one is pure chance.
It confirmed 1 transactions in 0.00 MB (0.0% of the 4 million weight-unit limit). The median transaction paid 0.00 sat/vB, and all fees added up to 0.0000 BTC. With the 50.000 BTC subsidy of halving era 1, Unknown earned 50.0000 BTC for this block.
Block 21 is number 22 of 2,016 in difficulty epoch 0; 1,994 blocks remain until the next difficulty adjustment at block 2,015. The next halving is at block 210,000, 209,979 blocks after this one.
Its hash starts with 8 zeros: that is the proof of work, a number below the target that the whole network’s hashrate had to search for. Unknown found 7 blocks in the week before. Today the block has 972,300 confirmations, so it is settled beyond any practical doubt.