Ask HN: What is the best number, and why?

3082010a02820101009cd30cf05ae52e47b7725d3783b3686330ead7352 61925e1bdbe35f170922fb7b84b4105aba99e350858ecb12ac468870ba3 e375e4e6f3a76271ba7981601fd7919a9ff3d0786771c8690e9591cffee 699e9603c48cc7eca4d7712249d471b5aebb9ec1e37001c9cac7ba705ea ce4aebbd41e53698b9cbfd6d3c9668df232a42900c867467c87fa59ab85 26114133f65e98287cbdbfa0e56f68689f3853f9786afb0dc1aef6b0d95 167dc42ba065b299043675806bac4af31b9049782fa2964f2a20252904c 674c0d031cd8f31389516baa833b843f1b11fc3307fa27931133d2d36f8 e3fcf2336ab93931c5afc48d0d1d641633aafa8429b6d40bc0d87dc3930 203010001

the let's encrypt public key.

2. It's the only even prime number.

Zero. Without which no number systems would make any sense.

And without it we wouldn't have a space programme because they always launch after 0.

The Romans seemed to get along OK without it.

666