311 is the number after 310 and before 312.

In mathematics

311 is a prime number, and a permutable prime with 113 and 131.

It can be expressed as a sum of consecutive primes in three different ways: as a sum of three consecutive primes (101 + 103 + 107), as a sum of five consecutive primes (53 + 59 + 61 + 67 + 71), and as a sum of seven consecutive primes (31 + 37 + 41 + 43 + 47 + 53 + 59).

311 is a strictly non-palindromic number, it is not palindromic in any base from base 2 to base 309.

Other uses

• 311 is the name of a band, see 311 (band).

• 311 is also used as a non-emergency "hot line" telephone number in some US cities, including Baltimore, Maryland and San Jose, California, as an alternative to 911 for emergency use. This in turn has led to the Madrid train bombings which occurred on March 11, 2004 being referred to as "311" by some journalists and commentators. For detailed information, see 3-1-1.

• For the year 311 AD, see 311.