115

115 = 5 x 23.

115 = 23 x (2 + 3).

115 has a unique representation as a sum of three squares: 3² + 5² + 9² = 115.

115 is the smallest three-digit integer, abc, such that (abc)/(a*b*c) is prime: 115/5 = 23.

STS-115 was a space shuttle mission to the International Space Station flown by the space shuttle Atlantis on Sept. 9, 2006.

Source: Prime Curios!

611

611 = 13 x 47.

611 is a brilliant number. It is a semiprime (product of two primes) whose prime factors have the same number of decimal digits. These numbers are generally used for cryptographic purposes and for testing the performance of prime factoring programs.

611 is a number n such that n times n + 5 gives the concatenation of a number m and itself: 611 x 616 = 376376.

611 is a number with no zeroes that becomes a prime when any one digit is deleted: 61 and 11 are both primes.

For customers of some telephone companies in Canada and in the United States, 611 is the abbreviated dialing telephone number used to report a problem with telephone service, or with a payphone.

Source: The On-Line Encyclopedia of Integer Sequences

76

76 = 2² x 19.

76 has a unique representation as the sum of three squares: 76 = 2² + 6² + 6².

76 is the ninth Lucas number. Lucas numbers are the sequence of integers obtained when each successive element is the sum of the previous two elements, starting with 1 and 3.

76 is the number of integer partitions of 21 into distinct parts. The partitions of an integer are the number of ways of writing that integer as a sum of positive integers without regard to order with the constraint that all integers in a given partition are distinct.

Meredith Wilson's song "Seventy-six Trombones" is a highlight of the musical The Music Man.

Source: Wolfram MathWorld

320

320 = 2⁶ x 5.

320 has a representation as the sum of two squares: 8² + 16² = 320.

320 is the maximum determinant of a 10 x 10 matrix of 0s and 1s.

320 is 500 in base 8.

There are 320 rods in a mile; 320 is also the number of fluid ounces in a peck.

Source: Number Gossip

713

713 = 23 x 31.

713 is a brilliant number because it is a semiprime (product of two primes) whose prime factors have the same number of decimal digits.

713 is the sum of three consecutive prime numbers: 713 = 233 + 239 + 241.

713 is the number of commutative monoids of order 7 with four idempotents. A monoid is a set that is closed under an associative binary operation and has an identity element. Unlike a group, its elements need not have inverses.

Telephone area code 713 serves the Houston area.

Source: What’s Special About This Number?

227

227 is a prime number.

227 and 229 form a twin prime pair.

227 is the number of composite days in a year.

227 is the smallest three-digit prime that is changed into a composite number if any digit is deleted.

227 is the number of connected planar graphs with eight edges.

227 was an NBC sitcom set in Washington, D.C., that ran from 1985 to 1990.

Source: Number Gossip

581

581 = 7 x 83.

581 is the sum of three consecutive primes: 191 + 193 + 197 = 581.

581 has a base 3 representation (210112) that begins with its base 4 representation (21011).

581 becomes a prime when 3 is prefixed or appended: 3581 and 5813 are primes.

Gliese 581 c was the first discovered terrestrial exosolar planet in the habitable zone surrounding its star (where the surface temperatures might be similar to Earth's).

Source: Wikipedia