Robert Franek wrote a book entitled The Best 331 Colleges.
The total population of Rives, Tennessee (the address of one of the authors), as of the 2000 census.
The total number of reduced quadratic forms having one class per genus. [Noe]
The United States conducted 331 atmospheric nuclear bomb tests before the test ban treaty of 1962. [McCranie]
331 = 11*13*17-2^2*3*5^2*7, using only the potential prime divisors (with multiplicity) up to the square root; and they use all of them. Can you find an expression for the next prime (337) in such a way? [Wood]
331 is the smallest prime that is good, happy, lucky, and cuban. [Green]
331 = (313) - (3*1*3) + (3^1^3). [Silva]
The only known exponent n such that 83^n-82^n is a (probable) prime. [Hasler]
The first prime to appear in the "commas sequence".
The smallest prime p such that the concatenation of p and p^2 is a Cyclops number (331109561). [Gaydos]
Add the cubes of the digits of p = 331, i.e. 1^3 + 3^3 + 3^3 + 1^3 = 55. Repeat the same steps with 55. It follows that 5^3 + 5^3 = 250, then 2^3 + 5^3 + 0^3 = 133, etc. Is 133 the only reversal of p in the sequence of primes? [Missailidis]
(There are 7 curios for this number that have not yet been approved by an editor.)