71 (number)

71 (seventy-one) is the natural number following 70 and preceding 72.

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In mathematics

71 is:
*the 20th prime number. The next is 73, with which it composes a twin prime.
*a permutable prime and emirp with 17.
*is the largest number which occurs as a prime factor of an order of a sporadic simple group.
*the sum of three consecutive primes: 19, 23 and 29.
*a centered heptagonal number.
*an Eisenstein prime with no imaginary part and real part of the form 3''n'' – 1.
*a Pillai prime, since 9! + 1 is divisible by 71 but 71 is not one more than a multiple of 9.
*the largest (15th) supersingular prime, which is also a Chen prime.
*part of the last known pair (71, 7) of Brown numbers, since 71² = 7! + 1.
*the twenty-third term of the Euclid–Mullin sequence, as it is the least prime factor of one more than the product of the first twenty-two terms.
*the smallest positive integer ''d'' such that the imaginary quadratic field Q() has class number = 7.
*the algebraic degree of Conway's constant, a remarkable number arising in the study of look-and-say sequences.
*the sum of primes less than 71 (2 through 67) is 568, which is divisible by 71.
*71 is the only number between 1 and 100 that is one less or one more than divisible by all numbers from 2 to 10 (70: 2, 5, 7, 10) (72: 2, 3, 4, 6, 8, 9).
*71 is an index of a prime Lucas number.

In science

*The atomic number of lutetium, a lanthanide

In astronomy

* Messier object M71, a magnitude 8.5 globular cluster in the constellation Sagitta
* The New General Cataloguebr>object
NGC 71, a magnitude 13.2 peculiar spiral galaxy in the constellation Andromeda

In other fields

Seventy-one is also:
* The number of different characters that can be used with a standard English keyboard, excluding uppercase letters
* The registry of the U.S. Navy's nuclear aircraft carrier USS ''Theodore Roosevelt'' (CVN-71), named after U.S. President Theodore Roosevelt
* The number of the French department Saône-et-Loire
* The year AD 71, 71 BC, or 1971
* In the Mexican television sitcom, ''El Chavo del Ocho'', Doña Clotilde lives in the apartment number 71, being therefore known as "La Bruja del 71" ( Spanish: "The Witch from Number 71")
* Lockheed SR-71 Blackbird long-range, Mach 3 strategic reconnaissance aircraft
* '' 71 Fragments of a Chronology of Chance'', a film by Michael Haneke
* '' 71: Into the Fire'', South Korean film about the Korean War
* The form number for the United States Office of Personnel Management for requesting a leave of absence
* The Irish Rail 071 Class diesel locomotive
* In the Jason Bourne novels by American author Robert Ludlum the department within the CIA which made Bourne and the other super agents is called Treadstone Seventy-One.
* SR-71, an American alternative rock band
* The number of the laps of the Austrian Grand Prix, Mexican Grand Prix, and Brazilian Grand Prix

References

{{Integers, zero

Integers