About block 646
Bitcoin block 646 was mined by Unknown on January 16, 2009 at 12:35 AM UTC, 8 min 9 s after block 645. 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 646 is number 647 of 2,016 in difficulty epoch 0; 1,369 blocks remain until the next difficulty adjustment at block 2,015. The next halving is at block 210,000, 209,354 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 8 blocks in the week before. Today the block has 971,981 confirmations, so it is settled beyond any practical doubt.