This number is a prime.

+ Band 311 (pronounced "three eleven") got their name from a police code after one of the band's former members was charged with indecent exposure. [Puckett]

+ The Federal Communications Commission (FCC) set aside the prime number 311, a telephone code now used in many U.S. Cities, for connection to police non-emergencies.

+ 311 is the eleventh three-digit prime for which the sum of the squares of its digits is also a prime. Note that the sum here is eleven as well. [Trotter]

+ 311 is the smallest number expressible as the sum of consecutive primes in four ways. [De Geest]

+ Apartment number 311 is the first door to be knocked on in the movie Ace Ventura: Pet Detective. [Shadyac]

+ Mickey Mantle's rookie card number 311 is prime. Note also that M+I+C+K+E+Y+M+A+N+T+L+E = 131 (A=1...Z=26), another prime which happens to contain the same digits as his rookie card number. [Rupinski]

+ A right-truncatable prime that can be obtained by concatenating the first three non-composite digits of π. [Necula]

+ The smallest three-digit prime that is the sum of three different three-digit primes. [Gallardo]

+ Lesser of the first occurrence of a twin prime (311, 313) such that sets of digits of both primes are equal. [Firoozbakht]

+ Timothy Leary claimed to have taken LSD a total of 311 times. [Coeburn]

+ The largest prime of the form |a^b - c^d|, where a, b, c and d are the first 4 primes. 311 = 7^3 - 2^5. Curiously, 311 = prime(2^6). [Post]

+ The only home emirp for two distinct composite numbers n <100, (cases n=9 and n=33). [Loungrides]

+ 311 trillion years is the span of a wide era called mahamantavara on the Vedic Hindu time scale. [Beedassy]

+ Sources of narrow spectrum radiation (UVB 311 nm) are considered to be the best for vitiligo and psoriasis treatment. [Homewood]

+ Describing this emirp (one 3, two 1) yields another (1321). [Silva]

+ The only prime (emirp) that can be represented as p p’s minus q q’s, where p, q are successive primes, i.e., 333-22. [Loungrides]

+ The Transportation Security Administration (TSA) has a "3-1-1" for carry-ons.

+ The smallest prime (emirp) that is the first of six consecutive primes that remain prime if you delete their first digit, i.e., 311, 313, 317, 331, 337, 347. [Loungrides]

+ "The End and the Beginning" begins on page 311 of Paulo's book Prime Numbers, Friends Who Give Problems.

+ The smallest prime p such that every integer from 2 to 10 is a quadratic residue mod p. [Ewing]

+ There are 3^11 different ways to tie the knot of a necktie. [Vejdemo-Johansson]

+ The smallest prime number that is an anagram of two smaller primes. [Gaydos]

+ The smallest emirp that can be represented as sum of the four powers a^a+b^b+c^c+d^d where abcd is a 4-digit prime p, i.e., (p=1433), with 1^1+4^4+3^3+3^3=311. [Loungrides]

+ 311 is the 64th prime number. The entire process from production to ejaculation of mature spermatozoa takes, on average, 64 days to complete. 311 is the standard gematria value of the Hebrew word איש ('iysh, pronounced, eesh), meaning, man or husband, who, according to Genesis 2:24 would “leave his father and mother, and cleave unto his wife: and they shall be one flesh.” Reference: D. Durairajanayagam et al., "Sperm Biology from Production to Ejaculation", 2015, DOI: 10.1007/978-1-4939-2140-9_5. [Vanualailai]

(There are 9 curios for this number that have not yet been approved by an editor.)

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