Significance of numbers and references in popular media

Does the number 742 (Evergreen Terrace, the home of the simpsons) have any other meaning?
Was it a random number chosen for the address or does it have any subtle (or not) significantce?
Also, is the double reference to “The Once and Future King” (A modern re-telling of Arthurian legend) supposed to imply subtlely that mutants are the modern day Merlin, (or that Merlin was merely an early mutant)?

According to Wikipedia, Charlemagne was born in 742. I seriously doubt there is any connection to The Simpsons though…

Just to clarify, your second question is in reference to the X-Men movies? When asking about references in works, it really helps to mention what work you’re asking about.

And I think that the dual appearance of the book is meant to illustrate the differences between Magneto’s and Xavier’s philosophies. Magneto is presumably focussing on the Divine Right of Kings aspect of the Arthur story, where Arthur, by virtue of being the supernaturally-proven heir to Uther Pendragon, is legitimately the ruler of the known world. Xavier, however, is more interested in the notion of “Might for right, not might makes right”, and sees the essential role of Arthur and of himself as a bringer of peace.