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==In mathematics==
==In mathematics==
191 is a [[prime number]], part of a [[prime quadruplet]] of four [[prime number|primes]]: 191, [[193 (number)|193]], [[197 (number)|197]], and [[199 (number)|199]].<ref>{{Cite OEIS|A136162|List of prime quadruplets {p, p+2, p+6, p+8} }}</ref> Because doubling and adding one produces another prime number (383), 191 is a [[Sophie Germain prime]].<ref>{{Cite OEIS|A005384|Sophie Germain primes p: 2p+1 is also prime}}</ref> It is the smallest prime that is not a [[full reptend prime]] in ''any'' base from 2 to 10; in fact, the smallest base for which 191 is a full period prime is [[base 19]].<ref>Wolfram MathWorld; [http://mathworld.wolfram.com/PrimitiveRoot.html Primitive Root]</ref>
* 191 is an [[Parity (mathematics)|odd number]]
* 191 is a [[centered polygonal number|centered 19-gonal number]]<ref>{{Cite web|url=https://oeis.org/A069132|title=Sloane's A069132 : Centered 19-gonal numbers|last=|first=|date=|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-28}}</ref>
* 191 is a [[deficient number]], as 1 is less than 191
* 191 is a [[Lazy caterer's sequence|lazy caterer]], number of slices a circle can be made into (19 slices can divide into 191 pieces)
* 191 is an [[Thue-Morse sequence|odious number]]
* 191 is a [[prime number]]
** [[Chen prime]]
** [[Eisenstein prime]] with no imaginary part
** [[Gaussian integer|Gaussian prime]]
** [[Palindromic prime]], in base 10
** Part of a [[prime quadruplet]] of four [[prime number|primes]]: 191, [[193 (number)|193]], [[197 (number)|197]], and [[199 (number)|199]]
** [[Sophie Germain prime]]
** [[Strong prime]]
** [[Twin prime]] that differs from another [[prime number]] ([[193 (number)|193]]) by [[2 (number)|2]]
** The smallest prime that is not a [[full reptend prime]] in ''any'' base from 2 to 10 – in fact the smallest base for which 191 is a full period prime is [[base 19]].<ref>Wolfram MathWorld; [http://mathworld.wolfram.com/PrimitiveRoot.html Primitive Root]</ref>
* 191 is a [[square-free]] number
* 191 is a [[Thabit number]]
* 191 is an [[undulating number]]
* 191 is the smallest positive integer ''d'' such that the imaginary [[quadratic field]] '''Q'''({{sqrt|–''d''}}) has [[Class number (number theory)|class number]] = 13.<ref>{{cite web|title=Tables of imaginary quadratic fields with small class number|website=numbertheory.org|url=http://www.numbertheory.org/classnos/}}</ref>

==In astronomy==
* [[191 Kolga]] is a large and dark [[Asteroid belt|Main belt]] [[asteroid]]
* [[3C 191]] is a [[quasar]] located in the [[constellation]] [[Cancer (constellation)|Cancer]]

==In emergency telephone numbers==
* 1-9-1 is the [[Emergency telephone number|emergency phone number]] in:
** [[Brazil]] for the [[Federal Highway Police (Brazil)|Federal Highway Police]]
** [[Ghana]] for the police
** [[Greece]] for a [[Wildfire|forest fire]]
** [[Thailand]] for the police
** [[France]] for the aeronautical emergencies
* In [[Australia]] dialing 191 will redirect you to 000, Australia's Emergency telephone number.

==In geography==
* [[191 Peachtree Tower]] at 191 [[Peachtree Street]] is the fourth tallest [[skyscraper]] in [[Atlanta]]
* [[191 North Wacker]] is a 37-story skyscraper in [[Chicago]]
* [[Marquis No. 191, Saskatchewan]] is a [[rural municipality]] in [[Saskatchewan]], Canada

==In the military==
* [[191st Air Refueling Squadron]] unit of the [[Utah Air National Guard]]
* [[191st Airlift Group]] unit the [[Michigan Air National Guard]] at [[Selfridge ANGB]], [[Michigan]]
* [[191st (South Alberta) Battalion, CEF|191st Battalion, CEF]] was a unit of the [[Canadian Expeditionary Force]] in [[Southern Alberta|Southern Alberta, Canada]]
* [[191st Infantry Brigade (United States)|191st Infantry Brigade]] formed as part of the [[United States Army Reserve]]'s [[95th Infantry Division (United States)|95th Division]]
* [[Focke-Wulf Fw 191]] was a prototype [[Germany|German]] bomber aircraft of [[World War II]]
* [[No. 191 Squadron RAF]] a [[Royal Air Force]] squadron from 1917–1919, and 1943–1945
* [[Special Order 191]] was a military order issued by [[Confederate Army]] [[General (CSA)|General]] [[Robert E. Lee]] in the [[Maryland Campaign]] of the [[American Civil War]]
* {{USNS|Benjamin Isherwood|T-AO-191}} is a [[United States Navy]] {{sclass-|Henry J. Kaiser|oiler|0}} [[fleet replenishment oiler]]
* {{USS|Coffman|DE-191}} was a United States Navy {{sclass-|Cannon|destroyer escort}} during World War II
* {{USS|Frigate Bird|AMS-191}} was a United States Navy {{sclass-|Bluebird|minesweeper}} during the 1950s
* {{USS|Lebanon|AK-191}} was a United States Navy C1-M-AV1-type cargo ship during World War II
* {{USS|Mason|DD-191}} was a United States Navy {{sclass-|Clemson|destroyer}} during World War II
* {{USS|Pondera|APA-191}} was a United States Navy {{sclass-|Haskell|attack transport}} during World War II
* {{USS|Sculpin|SS-191}} was a United States Navy {{sclass-|Sargo|submarine}} during World War II
* {{USS|Vandalia|IX-191}} was a United States Navy a twin-screw, steel-hulled [[Tanker (ship)|tanker]] during World War II
* [[VF-191]], "Satan's Kittens", was a fighter squadron of the United States Navy during World War II

==In movies==
* The 2008 movie “[https://www.imdb.com/title/tt1210348/ Highway 191]”

==In sports==
* [[Jordan 191]] was the first [[Formula One]] car built by [[Jordan Grand Prix]], and participated in the [[1991 Formula One season]]

==In transportation==
* [[RD-191]], a Russian high performance single-combustion chamber rocket engine
* [[191st Street (IRT Broadway – Seventh Avenue Line)]], a New York City Subway station at St. Nicholas Avenue in Manhattan served by the {{NYCS Broadway-Seventh north|time=nolink}} train
* At least five known plane crashes have involved [[Flight 191 (disambiguation)|flights numbered 191]]; as a result, the number is considered unlucky in the airline industry and has been withdrawn from use in some airlines

==In other fields==
''' 191''' is also:
* The year [[191|AD 191]] or [[191 BC]]
* The [[atomic number]] of an element temporarily called [http://www.flw.com/datatools/periodic/001.php?id=191 Unennunium]
* [[Minuscule 191]] is a [[Greek language|Greek]] [[Lower case|minuscule]] [[manuscript]] of the [[New Testament]], on parchment
* [[Bose Corporation|Bose]] [http://www.bose.com/controller?url=/shop_online/speakers/stereo_speakers/191_speakers/index.jsp&perfsourceid=k115513&src=k115513 Virtually Invisible 191] speakers


==See also==
==See also==
* [[191 (disambiguation)]]
* [[List of highways numbered 191]]
* [[United Nations Security Council Resolution 191]]
* [[List of United States Supreme Court cases, volume 191|United States Supreme Court cases, Volume 191]]
* [[Pennsylvania House of Representatives, District 191]]

==External links==
{{Commons category|191 (number)}}
* [https://web.archive.org/web/20040609064156/http://athensohio.net/reference/number/191/ Number Facts and Trivia: 191]
* [http://www.numdic.com/191 The Number 191]
* [http://www.numbergossip.com/191 Number Gossip: 191]
* [http://www.virtuescience.com/191.html VirtueScience: 191]
* [http://primes.utm.edu/curios/page.php?short=191 Prime Curios: 191]


== References ==
== References ==
{{Reflist}}
{{Reflist}}

{{Commons category}}
{{Integers|1}}
{{Integers|1}}


{{DEFAULTSORT:191 (Number)}}
{{DEFAULTSORT:191 (Number)}}
[[Category:Integers]]
[[Category:Integers]]


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Revision as of 20:51, 30 December 2022

← 190 191 192 →
Cardinalone hundred ninety-one
Ordinal191st
(one hundred ninety-first)
Factorizationprime
Primeyes
Greek numeralΡϞΑ´
Roman numeralCXCI
Binary101111112
Ternary210023
Senary5156
Octal2778
Duodecimal13B12
HexadecimalBF16

191 (one hundred [and] ninety-one) is the natural number following 190 and preceding 192.

In mathematics

191 is a prime number, part of a prime quadruplet of four primes: 191, 193, 197, and 199.[1] Because doubling and adding one produces another prime number (383), 191 is a Sophie Germain prime.[2] It is the smallest prime that is not a full reptend prime in any base from 2 to 10; in fact, the smallest base for which 191 is a full period prime is base 19.[3]

See also

References

  1. ^ Sloane, N. J. A. (ed.). "Sequence A136162 (List of prime quadruplets {p, p+2, p+6, p+8})". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  2. ^ Sloane, N. J. A. (ed.). "Sequence A005384 (Sophie Germain primes p: 2p+1 is also prime)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  3. ^ Wolfram MathWorld; Primitive Root