ⓘ 101 (number)

101 (number)

ⓘ 101 (number)

101 is the natural number following 100 and preceding 102.

It is variously pronounced "one hundred and one" / "a hundred and one", "one hundred one" / "a hundred one", and "one oh one". As an ordinal number, 101st one hundred first, rather than 101th, is the correct form.


1. In mathematics

101 is:

  • a palindromic number in base 10, and so a palindromic prime.
  • a Sexy prime since 107 and 113 are also prime, with which it makes a sexy prime triplet.
  • the only existing prime with alternating 1s and 0s in base 10 and the largest known prime of the form 10 n + 1.
  • a Chen prime since 103 is also prime, with which it makes a twin prime pair.
  • the sum of five consecutive primes 13 + 17 + 19 + 23 + 29.
  • an Eisenstein prime with no imaginary part and real part of the form 3 n − 1 {\displaystyle 3n-1}.
  • the 26th prime number.
  • a unique prime, because the period length of its reciprocal is unique among primes.
  • a centered decagonal number.
  • the fifth alternating factorial.

Given 101, the Mertens function returns 0. It is the second prime having this property.

For a 3-digit number in base 10, this number has a relatively simple divisibility test. The candidate number is split into groups of four, starting with the rightmost four, and added up to produce a 4-digit number. If this 4-digit number is of the form 1000 a + 100 b + 10 a + b where a and b are integers from 0 to 9, such as 3232 or 9797, or of the form 100 b + b, such as 707 and 808, then the number is divisible by 101.

On the seven-segment display of a calculator, 101 is both a strobogrammatic prime and a dihedral prime.


2. In science

  • In mineralogy, a Miller index of 101 is a crystal face that crosses the horizontal axis a and 3d vertical axis c but does not cross the 2d vertical axis b.
  • In astronomy it is the Messier designation given to the Pinwheel Galaxy in Ursa Major.
  • In physics and chemistry, it is the atomic number of mendelevium, an actinide.

3. In books

According to Books in Print, more books are now published with a title that begins with 101 than 100. They usually describe or discuss a list of items, such as 101 Ways to. or 101 Questions and Answers About. This marketing tool is used to imply that the customer is given a little extra information beyond books that include only 100 items. Some books have taken this marketing scheme even further with titles that begin with 102, 103, or 1001. The number is used in this context as a slang term when referring to "a 101 document" what is usually referred to as a statistical survey or overview of some topic.

Room 101 is a torture chamber in the novel Nineteen Eighty-Four by George Orwell.

Creative Writing 101 by Raymond Carver, "A writers values and craft. This was what the man John Gardner taught and what he stood for, and this is what Ive kept by me in the years since that brief but all important time."


4. In education

In American university course numbering systems, the number 101 is often used for an introductory course at a beginners level in a departments subject area. This common numbering system was designed to make transfer between colleges easier. In theory, any numbered course in one academic institution should bring a student to the same standard as a similarly numbered course at other institutions. The term was first introduced by the University of Buffalo in 1929.

Based on this usage, the term "101" has been extended to mean an introductory level of learning or a collection of introductory materials to a topic.


5. In other fields

  • For a new checking account in the US, the number of the first check.
  • 101 is the main Police Emergency Number in Belgium.
  • An HTTP status code indicating that the server is switching protocols as requested by the client to do so.
  • A term used to define the number of keys on a standard 101 key computer keyboard
  • Roi Et Province, a province in Thailand. The name is literally 101 in Thai language.
  • Lebanese Red Cross EMS Center at Spears is coded 101
  • 101 is the Single Non-Emergency Number SNEN in some parts of the UK, a telephone number used to call emergency services that are urgent but not emergencies. 101 is now available across all areas of England and Wales.
  • The Wonderful 101
  • Vault 101 is the starting area of Fallout 3
  • TV show Zoey 101
  • The Zastava 101 is a compact car by the former Yugoslav automaker.
  • 101 was the tail number of a Polish Air Force Tu-154, which crashed on 10 April 2010 whilst on its final approach to Smolensk North Airport killing all aboard including president Lech Kaczynski and his wife. See 2010 Polish Air Force Tu-154 crash.
  • In Hindu its lucky number.
  • Korean reality girl group survival show Produce 101
  • iCar 101 is a roadable aircraft design concept.
  • Depeche Mode - 101 album
  • 101 Ranch Oil Company
  • Taipei 101, the tallest skyscraper in the world from 2004 to 2010.
  • 101 is the identifying number of several infantry units in various militaries across the world, such as the American and Israeli paratrooper brigades
  • "lordre des Piliers du 101" is an important student association in Belgium since 1977.
  • Highways numbered 101, the longest and most well-known of which is U.S. Route 101.
  • 101st kilometre, a condition of release from the Gulag in the Soviet Union.
  • 101 Dalmatians
  • Charter of the French Language, Bill 101.

  • Arizona State Route 101 or Loop 101 is a semi - beltway encompassing much of the Phoenix Metropolitan Area in the United States. It connects several suburbs
  • album s title the performance was the 101 st and final performance of the tour and coincidentally also the number of a famous highway in the area The
  • U.S. Route 101 US 101 is a major north south United States Numbered Highway, stretching from Los Angeles, California to Tumwater, Washington. The California
  • Entertainment System. The NES - 101 control deck came packaged with a redesigned version of the standard NES controller model number NES - 039 shaped very similarly
  • King s Highway 101 commonly referred to as Highway 101 is a provincially maintained highway in the Canadian province of Ontario. The 473.3 - kilometre
  • US Army 101 is a 2 - 8 - 0 steam locomotive that was originally operated by the United States Army. It is one of two survivors of the 1, 500 General Pershing
  • The Agusta A. 101 originally designated AZ. 101 was a large prototype transport helicopter developed in Italy during the course of the 1960s. Despite
  • two is the natural number following 101 and preceding 103. 102 is an abundant number and semiperfect number It is a sphenic number It is the sum of four
  • German submarine U - 101 was a Type VIIB U - boat of Nazi Germany s Kriegsmarine during World War II. She had a highly successful career. German Type VIIB
  • The McDonnell CF - 101 Voodoo was an all - weather interceptor aircraft operated by the Royal Canadian Air Force and the Canadian Forces between 1961 and

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