84 (eighty-four) is the

natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called ''cardinal ...

following 83 and preceding 85.

In mathematics

84 is: * the sum of the first seven

triangular number A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples being square numbers and cube numbers. The th triangular number is the number of dots i ...

s (making it a

tetrahedral number A tetrahedral number, or triangular pyramidal number, is a figurate number that represents a pyramid with a triangular base and three sides, called a tetrahedron. The th tetrahedral number, , is the sum of the first triangular numbers, that is, ...

). * a Dodecahedral number. * the sum of a

twin prime A twin prime is a prime number that is either 2 less or 2 more than another prime number—for example, either member of the twin prime pair (41, 43). In other words, a twin prime is a prime that has a prime gap of two. Sometimes the term ''twin p ...

(41 + 43). * a

semiperfect number In number theory, a semiperfect number or pseudoperfect number is a natural number ''n'' that is equal to the sum of all or some of its proper divisors. A semiperfect number that is equal to the sum of all its proper divisors is a perfect number. ...

, being thrice a perfect number. * a palindromic number and a

repdigit In recreational mathematics, a repdigit or sometimes monodigit is a natural number composed of repeated instances of the same digit in a positional number system (often implicitly decimal). The word is a portmanteau of repeated and digit. Example ...

in bases 11 (77₁₁), 13 (66₁₃), 20 (44₂₀), 27 (33₂₇), and 41 (22₄₁). * the

lim sup In mathematics, the limit inferior and limit superior of a sequence can be thought of as limiting (that is, eventual and extreme) bounds on the sequence. They can be thought of in a similar fashion for a function (see limit of a function). For ...

of the largest finite subgroup of the

mapping class group In mathematics, in the subfield of geometric topology, the mapping class group is an important algebraic invariant of a topological space. Briefly, the mapping class group is a certain discrete group corresponding to symmetries of the space. Mo ...

of a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''g'' surface divided by ''g''. A hepteract is a seven-

dimension In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coor ...

al hypercube with 84

penteract In five-dimensional geometry, a 5-cube is a name for a five-dimensional hypercube with 32 vertices, 80 edges, 80 square faces, 40 cubic cells, and 10 tesseract 4-faces. It is represented by Schläfli symbol or , constructed as 3 tesseract ...

5-faces.

In astronomy

Messier object The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only in ...

M84, a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

11.0

lenticular galaxy A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. ...

in the constellation

Virgo Virgo may refer to: *Virgo (astrology), the sixth astrological sign of the zodiac * Virgo (constellation), a constellation *Virgo Cluster, a cluster of galaxies in the constellation Virgo *Virgo Stellar Stream, remains of a dwarf galaxy * Virgo Su ...

*The New General Cataloguebr>object
NGC 84, a single star in the constellation Andromeda

In other fields

Eighty-four is also: * The year AD 84,

84 BC __NOTOC__ Year 84 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Carbo and Cinna (or, less frequently, year 670 ''Ab urbe condita''). The denomination 84 BC for this year has been used s ...

, or

1984 Events January * January 1 – The Bornean Sultanate of Brunei gains full independence from the United Kingdom, having become a British protectorate in 1888. * January 7 – Brunei becomes the sixth member of the Association of Southeas ...

. * The number of years in the , a cycle used in the past by Celtic peoples, equal to 3 cycles of the

Julian Calendar The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandr ...

and to 4

Metonic cycle The Metonic cycle or enneadecaeteris (from grc, ἐννεακαιδεκαετηρίς, from ἐννεακαίδεκα, "nineteen") is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The rec ...

s and 1

octaeteris In astronomy, an octaeteris (, plural: octaeterides) is the period of eight solar years after which the moon phase occurs on the same day of the year plus one or two days. This period is also in a very good synchronicity with five Venusian visibi ...

* The

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...

polonium Polonium is a chemical element with the symbol Po and atomic number 84. Polonium is a chalcogen. A rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character ...

* The model number of

Harpoon missile The Harpoon is an all-weather, over-the-horizon, anti-ship missile manufactured by McDonnell Douglas (now Boeing Defense, Space & Security). The AGM-84E Standoff Land Attack Missile (SLAM) and later AGM-84H/K SLAM-ER (Standoff Land Attack ...

WGS 84 The World Geodetic System (WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS. The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also descri ...

- The latest revision of the

World Geodetic System The World Geodetic System (WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS. The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also descr ...

, a fixed global reference frame for the Earth. * The house number of

84 Avenue Foch 84 Avenue Foch (german: Avenue Foch vierundachtzig) was the Parisian headquarters of the '' Sicherheitsdienst'' (SD), the counter-intelligence branch of the SS during the German occupation of Paris in World War II. Avenue Foch is a wide res ...

* The number of the French department

Vaucluse Vaucluse (; oc, Vauclusa, label= Provençal or ) is a department in the southeastern French region of Provence-Alpes-Côte d'Azur. It had a population of 561,469 as of 2019.code for international direct dial Country calling codes or country dial-in codes are telephone number prefixes for reaching telephone subscribers in the networks of the member countries or regions of the International Telecommunication Union (ITU). The codes are defined by the ...

phone calls to

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

* The town of Eighty Four,

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

* The company

84 Lumber 84 Lumber is an operated American building materials supply company. Founded in 1956 by Joseph Hardy, it derives its name from the unincorporated village of Eighty Four, Pennsylvania, a census-designated place south of Pittsburgh, where its ...

* The

ISBN The International Standard Book Number (ISBN) is a numeric commercial book identifier that is intended to be unique. Publishers purchase ISBNs from an affiliate of the International ISBN Agency. An ISBN is assigned to each separate edition an ...

Group Identifier for books published in

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

* A variation of the game 42 played with two sets of

dominoes Dominoes is a family of tile-based games played with gaming pieces, commonly known as dominoes. Each domino is a rectangular tile, usually with a line dividing its face into two square ''ends''. Each end is marked with a number of spots (also c ...

. * The film '' 84 Charing Cross Road'' (1987) starring

Anne Bancroft Anne Bancroft (born Anna Maria Louisa Italiano; September 17, 1931 – June 6, 2005) was an American actress. Respected for her acting prowess and versatility, Bancroft received an Academy Award, three BAFTA Awards, two Golden Globe Awards, two ...

and

Anthony Hopkins Sir Philip Anthony Hopkins (born 31 December 1937) is a Welsh actor, director, and producer. One of Britain's most recognisable and prolific actors, he is known for his performances on the screen and stage. Hopkins has received many accolad ...

KKNX KKNX (840 AM) is a classic hits radio station broadcasting to the Eugene, Oregon, area on 840 AM. 840 AM is a United States clear-channel frequency, on which WHAS in Louisville, Kentucky is the dominant Class A station. KKNX must reduce ni ...

Radio 84 in Eugene, Oregon * The B-Side to "Up All Night" (Take That song) * British Army term for the 84mm

Carl Gustav recoilless rifle The Carl Gustaf 8.4 cm recoilless rifle (, named after ''Carl Gustafs Stads Gevärsfaktori'' which initially produced it) is a Swedish developed caliber man-portable shoulder-fired recoilless rifle, initially developed by the Royal Swedish ...

. * How many Earth years it takes

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...

to orbit the sun once * The total number of Vertcoin to be released is 84 million “

Vertcoin Vertcoin ( Abbreviation: VTC) is an open-source cryptocurrency created in early 2014, that focuses on decentralization. Vertcoin uses an ASIC resistant proof-of-work mechanism to issue new coins and incentivize miners to secure the network and ...

”

References

{{Integers, zero Integers

In mathematics

In astronomy

In other fields

See also

References