In my December diary I posed the traditional year-end brain-teaser.
Find something curious or interesting to say about the number 2011.
Everybody and his granny emailed in to tell me that not only is 2011 a prime number itself, it is the sum of eleven consecutive primes. (And eleven is also a prime.) The topic is covered here, with many interesting side notes in the text and the comment thread. Did you know, for example (I didn't) that: "On average, roughly 70 percent of the natural numbers can be represented as a sum of consecutive primes in at least one way. This was proven by Moser in 1963." (That one's in the comments.)
This is also, as The Economist observed, a year of palindromes.