About block 3,521
Bitcoin block 3,521 was mined by Unknown on February 8, 2009 at 6:13 PM UTC, 8 min 11 s after block 3,520. 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 3,521 is number 1,506 of 2,016 in difficulty epoch 1; 510 blocks remain until the next difficulty adjustment at block 4,031. The next halving is at block 210,000, 206,479 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 12 blocks in the week before. Today the block has 970,482 confirmations, so it is settled beyond any practical doubt.