231 (two hundred
ndthirty-one) 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
230
Year 230 ( CCXXX) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Agricola and Clementinus (or, less frequently, year 983 '' Ab urbe ...
and preceding
232.
In mathematics
Two hundred
ndthirty-one 231 = 3·7·11, sphenic number,
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 ...
,
doubly triangular number,
hexagonal number
A hexagonal number is a figurate number. The ''n''th hexagonal number ''h'n'' is the number of ''distinct'' dots in a pattern of dots consisting of the ''outlines'' of regular hexagons with sides up to n dots, when the hexagons are overlaid so ...
,
octahedral number
In number theory, an octahedral number is a figurate number that represents the number of spheres in an octahedron formed from close-packed spheres. The ''n''th octahedral number O_n can be obtained by the formula:.
:O_n=.
The first few octahed ...
,
centered octahedral number
A centered octahedral number or Haüy octahedral number is a figurate number that counts the number of points of a three-dimensional integer lattice that lie inside an octahedron centered at the origin. The same numbers are special cases of t ...
, the number of integer
partitions of 16,
Mertens function
In number theory, the Mertens function is defined for all positive integers ''n'' as
: M(n) = \sum_^n \mu(k),
where \mu(k) is the Möbius function. The function is named in honour of Franz Mertens. This definition can be extended to positive re ...
returns 0,
and is the number of cubic inches in a U.S. liquid
gallon
The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use:
*the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Austr ...
.
In other fields
231 is:
* The year A.D.
231 or
231 BC.
* +231 is the
country code
Country codes are short alphabetic or numeric geographical codes (geocodes) developed to represent countries and dependent areas, for use in data processing and communications. Several different systems have been developed to do this. The term ...
for
Liberia.
* ''
Pacific 231'', an orchestral work by French composer
Arthur Honegger
Arthur Honegger (; 10 March 1892 – 27 November 1955) was a Swiss composer who was born in France and lived a large part of his life in Paris. A member of Les Six, his best known work is probably ''Antigone'', composed between 1924 and 1927 t ...
.
* ''
Pacific 231'', a 1949 short film directed by
Jean Mitry
Jean-René Pierre Goetgheluck Le Rouge Tillard des Acres de Presfontaines, whose pseudonym was Jean Mitry (; 7 November 1904 – 18 January 1988), was a French film theorist, critic and filmmaker, a co-founder of France's first film society, and, ...
.
*
List of highways numbered 231
References
Integers
{{Num-stub