27 (number)

• Twenty-seven is a cube of 3: ${\displaystyle 3^{3}=3\times 3\times 3}$.

• 27 is the second non-unitary cube prime of the form p³

• with a prime aliquot sum of 13; itself a semiprime, within an aliquot sequence of one composite number; (27,13,1,0) to the Prime in the 13-aliquot tree.

• 27 is also ²3 (see tetration). There are exactly 27 straight lines on a smooth cubic surface, which give a basis of the fundamental representation of the E₆ Lie algebra. 27 is also a decagonal number.[1]
• 27 is the value of the expression ${\displaystyle n^{n}}$, where ${\displaystyle n=3}$.
• In decimal, it is the first composite number not divisible by any of its digits.
• It is the radix (base) of the septemvigesimal positional numeral system.
• In decimal, 27 is the only positive integer that is three times the sum of its digits.
• In a prime reciprocal magic square of the multiples of 1/7, the magic constant is 27.
• Including the null-motif, there are 27 distinct hypergraph motifs. [2]
• In the Collatz conjecture (aka the "${\displaystyle 3n+1}$ conjecture"), a starting value of 27 requires 111 steps to reach 1, more than any number smaller than it.
• The unique simple formally real Jordan algebra, the exceptional Jordan algebra of self-adjoint 3 by 3 matrices of quaternions, is 27-dimensional.[3]
• In decimal, it is a Smith number[4] and a Harshad number.[5]
• It is located at the twenty-eighth (and twenty-ninth) digit after the decimal point in π. (3.141592653589793238462643383279...). If one starts counting with 0, it is one of few known self-locating strings in pi.
• In decimal, 27 is the sum of the numbers between and including its digits (${\displaystyle 2+3+4+5+6+7=27}$).
• There are 27 sporadic groups, if the Tits group is included.
• If one cyclically rotates the digits of a three-digit number that is a multiple of 27, the new number is also a multiple of 27. For example, 378, 783, and 837 are all divisible by 27.
• Any multiple of 27 with "000" or "999" inserted yields another multiple of 27. For example, 20007, 29997, 50004, and 59994 are all multiples of 27.
• Any multiple of 27 can be mirrored and spaced with a zero each for another multiple of 27. For example, 27 and 702, 54 and 405, and 378 and 80703 are all multiples of 27.
• In senary, one can readily test for divisibility by 43 (decimal 27) by seeing if the last three digits of the number match 000, 043, 130, 213, 300, 343, 430, or 513.
• 27 is divisible by the number of prime numbers below it, nine.

• The atomic number of cobalt.
• Dark matter is thought to make up 27% of the universe.[6]
• 27 is the number of bones in the human hand.[7]

• The number of letters in the Spanish alphabet.[10]
• The number of books in the New Testament.
• The total number of letters in the Hebrew alphabet (22 regular letters and 5 final consonants).
• Alternate name for The Hunt, a book by William Diehl.
• Abbé Faria's prisoner number in the book The Count of Monte Cristo.
• In Stephen King's novel It, It returns every 27 years to Derry.

• 27 Nakṣatra or lunar mansions in Hindu astrology.

• The value of all the colors in snooker add up to 27.
• The number of outs in a regulation baseball game for each team at all adult levels, including professional play, is 27.
• The New York Yankees have won 27 World Series championships, the most of any team in the MLB.

Twenty-seven is also:

• A-27, American attack aircraft.
• The code for international direct-dial phone calls to South Africa.
• The name of a cigarette, Marlboro Blend No. 27.
• The number of the French department Eure.
• One of the anthropomorphic math symbols Lisa Simpson imagines talking to her in The Simpsons episode "Girls Just Want to Have Sums", which, instead of offering the expected pun-based aphorism, rather unhelpfully only says "twenty seven".
• Number of planets needed to fuel the Reality Bomb in the episodes "The Stolen Earth" and "Journey's End" of Doctor Who (series 4).

• List of highways numbered 27
• List of highways numbered 27A

• Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987), p. 106.
• Mystery of the number 27 - Large collection of 27 related trivia and facts.
• Prime Curios! 27 from the Prime Pages
• The 27 Project - collection of 27 sightings in movies, TV, culture and art