21 - the number of the bus that takes you from Portsmouth Harbour to Havant bus station (I see as trend starting here )
23 - The London to Brighton Veteran Car Run is the longest-running motoring event in the world and folows the old A23 road
27 Club - those musicians who have died at the age of 27 (usually drug or alcohol related), including Brian Jones, Jim Morrison, Jimi Hendrix, JanisJoplin, Kurt Cobain and Amy Winehouse
...... and the year/s after that, after which they'll come along in such rapid succession that it's easier to just stick to one number and go with that for a few decades
33 - 33 was the number that was discovered to lead to the essential meaning of life (the Bible) in Dan Brown's 2009 novel "The Lost Symbol"
36 is both the square of 6 and a triangular number, making it a square triangular number. It is the smallest square triangular number other than 1 I also have absolutely no idea what that means