# 71 (number)

From HandWiki

__: Natural number__

**Short description**
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Cardinal | seventy-one | |||

Ordinal | 71st (seventy-first) | |||

Factorization | prime | |||

Prime | 20th | |||

Divisors | 1, 71 | |||

Greek numeral | ΟΑ´ | |||

Roman numeral | LXXI | |||

Binary | 1000111_{2} | |||

Ternary | 2122_{3} | |||

Quaternary | 1013_{4} | |||

Quinary | 241_{5} | |||

Senary | 155_{6} | |||

Octal | 107_{8} | |||

Duodecimal | 5B_{12} | |||

Hexadecimal | 47_{16} | |||

Vigesimal | 3B_{20} | |||

Base 36 | 1Z_{36} |

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

## In mathematics

**71** is:

- the 20th prime number. The next is 73, with which it composes a twin prime.
- a permutable prime 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.
^{[1]} - 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.
^{[2]} - the largest (15th) supersingular prime, which is also a Chen prime.
^{[3]} - part of the last known pair (71, 7) of Brown numbers, since 71
^{2}= 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.
^{[4]} - the smallest positive integer
*d*such that the imaginary quadratic field**Q**(√–*d*) has class number = 7.^{[5]} - 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.
^{[6]}

## 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 Catalogue 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
*United States*alternative rock band - The number of the laps of the Austrian Grand Prix, Mexican Grand Prix, and Brazilian Grand Prix

## References

- ↑ "Sloane's A069099 : Centered heptagonal numbers". OEIS Foundation. https://oeis.org/A069099.
- ↑ "Sloane's A063980 : Pillai primes". OEIS Foundation. https://oeis.org/A063980.
- ↑ "Sloane's A002267 : The 15 supersingular primes". OEIS Foundation. https://oeis.org/A002267.
- ↑ "Sloane's A000945 : Euclid-Mullin sequence". OEIS Foundation. https://oeis.org/A000945.
- ↑ "Tables of imaginary quadratic fields with small class number". http://www.numbertheory.org/classnos/.
- ↑ "Indices of prime Lucas numbers:". OEIS Foundation. https://oeis.org/A001606.

Original source: https://en.wikipedia.org/wiki/71 (number).
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