27 (number)

← 26 27 28 →
← 20 21 22 23 24 25 26 27 28 29 → List of numbers Integers ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	twenty-seven
Ordinal	th
Factorization	$3^{3}$
Divisors	1, 3, 9, 27
Greek numeral	ΚΖ´
Roman numeral	XXVII
Binary	110112
Ternary	10003
Senary	436
Octal	338
Duodecimal	2312
Hexadecimal	1B16

27 (twenty-seven) is the natural number following 26 and preceding 28. Twenty-seven is the smallest positive integer requiring four syllables to name in English, though it can be unambiguously defined in just two: "three cubed."

In mathematics

Twenty-seven is a perfect cube, being 3³ = 3 × 3 × 3. 27 is therefore the second smallest cube of a prime number. 27 is 3↑↑2 (using Knuth's up-arrow notation). There are exactly 27 straight lines on a smooth cubic surface. 27 is also a decagonal number.

27 has an aliquot sum of 13 and is the first composite member of the 13-aliquot tree with the aliquot sequence (27,13,1,0). Twenty-seven is the aliquot sum of the two odd discrete biprimes 69 and 133.

In base 10, it is the first composite number not evenly divisible by any of its digits. It is the radix (base) of the septemvigesimal positional numeral system.

In a prime reciprocal magic square of the multiples of 1/7, the magic constant is 27.

In the Collatz conjecture (aka the "3n + 1 conjecture") a starting value of 27 requires 112 steps to reach 1, many more than any lower number.

The unique simple formally real Jordan algebra, the exceptional Jordan algebra of self-adjoint 3 by 3 matrices of quaternions, is 27-dimensional.

In base 10, it is a Smith number and a Harshad number.

It is the twenty-eighth (and twenty-ninth) digit in π. (3.141592653589793238462643383279...).

If you start counting with 0 it is considered one of few Self-Locating strings in pi.

In science

• The atomic number of cobalt.

Astronomy

• The Messier object M27, a magnitude 7.5 planetary nebula in the constellation Vulpecula, also known as the Dumbbell Nebula.
• The New General Catalogue object NGC 27, a spiral galaxy in the constellation Andromeda
• The Saros number of the solar eclipse series which began on -1993 March 9 and ended on -713 April 16. The duration of Saros series 27 was 1280.1 years, and it contained 72 solar eclipses. Further, the Saros number of the lunar eclipse series which began on -1944 July 17 and ended on -411 January 23. The duration of Saros series 27 was 1532.5 years, and it contained 86 lunar eclipses.
• The 27th moon of Jupiter is Sinope.
• Uranus has 27 moons

Electronics

• The type 27 vacuum tube (valve), a triode introduced in 1927, was the first tube mass produced for commercial use to incorporate an indirectly heated cathode. This made it the first vacuum tube that could function as a detector in AC-powered radios. Prior to the introduction of the 27, home radios were powered by a set of three or more storage batteries with voltages of 3 volts to 135 volts.

In religion

• There are a total of 27 books in the New Testament

In music

Many famous rock/blues musicians died at age 27 (such as Jimi Hendrix and Kurt Cobain), often referred to as the 27 Club.

There are many songs titled just "Twenty-Seven," so it will suffice to list the most famous: a song by Scottish band Biffy Clyro from their 2002 album, Blackened Sky; the song by the Dave Matthews Band "#27," which they began playing on their 2007 summer tour; the Lagwagon song on their album Double Plaidinum.

The number also occurs buried in the lyrics without occurring in the title. American parodist "Weird Al" Yankovic hides the number in many of his songs and videos. Ben Weasel also likes to include the number in his songs for his bands Screeching Weasel and The Riverdales.

In the United States, the number 27 is associated with the East Bay punk scene.

In other fields

Twenty-seven is also:

• Gilles Villeneuve's famous Ferrari number now adopted by his son, Formula One World Champion Jacques Villeneuve in his NASCAR debut.
• Right Fielder of the Los Angeles Angels of Anaheim Vladimir Guerrero's Major League Baseball jersey number
• The total number of letters in the Hebrew alphabet (22 regular letters and 5 final consonants)
• The current number of Amendments to the United States Constitution.
• The modal age of the peak performance year for major league baseball position players, according to a commonly accepted theory by sabermetrician Bill James
• The code for international direct-dial phone calls to South Africa
• The designation (I-27) of a US interstate highway in Texas
• The designation (US 27) of a United States national highway from Fort Wayne, Indiana to Miami, Florida
• The name of a popular cigarette, Marlboro Blend No. 27
• The number of outs in a regulation Professional baseball game for each team.
• "The Bankers Case" on the U.S. Version of Deal or No Deal
• The name of a book by William Diehl, "27".
• In John Steinbecks novel "Cannery Row," Doc gives October 27th as his fake birthday.

Historical years

27 A.D., 27 B.C., 1927, 2027, etc.

References

• 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
• League of 27 - 27 forum