87 (number)

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← 80 81 82 83 84 85 86 87 88 89 → List of numbers ; Integers ; ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	eighty-seven
Ordinal	87th; (eighty-seventh)
Factorization	3 × 29
Divisors	1, 3, 29, 87
Greek numeral	ΠΖ´
Roman numeral	LXXXVII
Binary	10101112
Ternary	100203
Senary	2236
Octal	1278
Duodecimal	7312
Hexadecimal	5716

Last updated April 24, 2024

87 (eighty-seven) is the natural number following 86 and preceding 88.

In mathematics

87 is:

the sum of the squares of the first four primes (87 = 2² + 3² + 5² + 7²).
the sum of the sums of the divisors of the first 10 positive integers.^[1]
the thirtieth semiprime,^[2] and the twenty-sixth distinct semiprime^[3] and the eighth of the form (3.q).
together with 85 and 86,^[4] forms the last semiprime in the 2nd cluster of three consecutive semiprimes; the first comprising 33, 34, 35.
with an aliquot sum of 33; itself a semiprime, within an aliquot sequence of five composite numbers (87,33,15,9,4,3,1,0) to the Prime in the 3-aliquot tree.
5! - 4! - 3! - 2! - 1! = 87
the last two decimal digits of Graham's number.

In sports

Cricket in Australia holds 87 as a superstitiously unlucky score and is referred to as "the devil's number". This originates from the fact that 87 is 13 runs short of a century. 187, 287, and so on are also considered unlucky but are not as common as 87 on its own.^[5]
In the National Hockey League, Wayne Gretzky scored a league-high 87 goals with the Edmonton Oilers in the 1983–84 NHL season.

In other fields

Eighty-seven is also:

The atomic number of francium.
An answer to a popular puzzle question states 16, 06, 68, 88, xx, 98. The answer is 87 when looked upside down.
The number of years between the signing of the U.S. Declaration of Independence and the Battle of Gettysburg, immortalized in Abraham Lincoln's Gettysburg Address with the phrase " Four Score and Seven Years ago..."
The model number of Junkers Ju 87.
The number of the French department Haute-Vienne.
The code for international direct dial phone calls to Inmarsat and other services.
The 87 photographic filter blocks visible light, allowing only infrared light to pass.
The ISBN Group Identifier for books published in Denmark.
The opus number of the 24 Preludes and Fugues of Dmitri Shostakovich.
In model railroading, the ratio of the popular H0 scale is 1:87.^[6] Proto:87 scale claims to offer precise proportions of wheels and tracks of real railroads.
David Bowie CD (1987) Never Let Me Down includes the song, "'87 and Cry".
The 87th United States Congress met from January 3, 1961, to January 3, 1963, during John F. Kennedy's time in office.
Ed McBain's 87th Precinct: Lightning film starred Randy Quaid (1995).
Wenger Swiss Army Knife version XXL, listed in the Guinness Book of World Records as the world's most multi-functional penknife with 87 tools.
Sonnet 87 by William Shakespeare.
Vault 87 is a main location in the game Fallout 3 .
M87* is the first black hole ever photographed.
Aragorn's age in The Lord of the Rings .
"The Bite of '87" in the Five Nights at Freddy's series.

Related Research Articles

10 (ten) is the even natural number following 9 and preceding 11. Ten is the base of the decimal numeral system, the most common system of denoting numbers in both spoken and written language.

15 (fifteen) is the natural number following 14 and preceding 16.

21 (twenty-one) is the natural number following 20 and preceding 22.

111 is the natural number following 110 and preceding 112.

33 (thirty-three) is the natural number following 32 and preceding 34.

38 (thirty-eight) is the natural number following 37 and preceding 39.

69 (sixty-nine) is the natural number following 68 and preceding 70. An odd number and a composite number, 69 is divisible by 1, 3, 23 and 69. 69 is a semiprime because it is a natural number that is the product of exactly two prime numbers, and an interprime between the numbers of 67 and 71. Because 69 is not divisible by any square number other than 1, it is categorised as a square-free integer. 69 is also a Blum integer since the two factors of 69 are both Gaussian primes. In number theory, 69 is a deficient number, arithmetic number and a congruent number.

35 (thirty-five) is the natural number following 34 and preceding 36.

82 (eighty-two) is the natural number following 81 and preceding 83.

85 (eighty-five) is the natural number following 84 and preceding 86.

86 (eighty-six) is the natural number following 85 and preceding 87.

34 (thirty-four) is the natural number following 33 and preceding 35.

55 (fifty-five) is the natural number following 54 and preceding 56.

57 (fifty-seven) is the natural number following 56 and preceding 58.

58 (fifty-eight) is the natural number following 57 and preceding 59.

216 is the natural number following 215 and preceding 217. It is a cube, and is often called Plato's number, although it is not certain that this is the number intended by Plato.

177 is the natural number following 176 and preceding 178.

888 is the natural number following 887 and preceding 889.

99 (ninety-nine) is the natural number following 98 and preceding 100.

262 is a natural number preceded by the number 261 and followed by 263. It has the prime factorization 2·131.

References

↑ Sloane, N. J. A. (ed.). "SequenceA024916(sum_{k=1..n} sigma(k) where sigma(n) = sum of divisors of n)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
↑ "A001358 - OEIS". oeis.org. Retrieved 2020-08-10.
↑ "A006881 - OEIS". oeis.org. Retrieved 2020-08-10.
↑ Sloane, N. J. A. (ed.). "SequenceA056809". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
↑ Ferris, Sam (2014-11-02). "The real story behind Australia's unlucky number 87". cricket.com.au. Retrieved 2022-01-27.
↑ "Guide to model railroading scales and gauges". Model Railroader . 2 November 2011. Archived from the original on 22 June 2015. Retrieved 2 October 2016.

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[1] Sloane, N. J. A. (ed.). "SequenceA024916(sum_{k=1..n} sigma(k) where sigma(n) = sum of divisors of n)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.

[2] "A001358 - OEIS". oeis.org. Retrieved 2020-08-10.

[3] "A006881 - OEIS". oeis.org. Retrieved 2020-08-10.

[4] Sloane, N. J. A. (ed.). "SequenceA056809". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.

[5] Ferris, Sam (2014-11-02). "The real story behind Australia's unlucky number 87". cricket.com.au. Retrieved 2022-01-27.

[6] "Guide to model railroading scales and gauges". Model Railroader . 2 November 2011. Archived from the original on 22 June 2015. Retrieved 2 October 2016.

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