General fact: 138 is the number of constellations of the Triakis tetrahedron.
Mathematical fact: 138 is the sum of four consecutive primes (29 + 31 + 37 + 41).
Trivia: 138 is essendon's losing margin against Adelaide in round 10 of the 2006 AFL season.
Historical date: May 17th is the day in 1814 that the Constitution of Norway is signed and the Danish Crown Prince Christian Frederik is elected King of Norway by the Norwegian Constituent Assembly.