89 (NUMBER)

'89' ('eighty-nine') is the natural number following 88 and preceding 90.

Cardinal	89 eighty-nine
Ordinal	89th eighty-ninth
Factorization	$prime$
Divisors	1, 89
Roman numeral	LXXXIX
Binary	01011001
Hexadecimal	59

Contents

In mathematics

In science

In astronomy

In other fields

References

In mathematics

'Eighty-nine' is the 24th prime number, following 83 and preceding 97. 89 is a Chen prime. It is the smallest Sophie Germain prime to start a Cunningham chain of the first kind of six terms, {89, 179, 359, 719, 1439, 2879}. 89 is an Eisenstein prime with no imaginary part and real part of the form $3n\; -\; 1$.
89 is a Fibonacci number. Its reciprocal has a curious relationship to the Fibonacci sequence F(n):

89 is also a Markov number, appearing in solutions to the Markov Diophantine equation with other odd-indexed Fibonacci numbers.
Being the solution to ''x'' - φ(''x'') more often than any lower number, 89 is a highly cototient number.
Although 89 is a prime number, all of its digits,(8,9), are composite.
Although 89 is not a Lychrel number in base 10, it is unusual that it takes 24 iterations of the reverse and add process to reach a palindrome. Among the known non-Lychrel numbers in the first 10000 integers, no other number requires that many or more iterations. The palindrome reached is also unusually large.^[1]

In science

★ The atomic number of actinium.

In astronomy

★ Messier object M89, a magnitude 11.5 elliptical galaxy in the constellation Virgo.

★ The New General Catalogue object NGC 89, a magnitude 13.5 peculiar spiral galaxy in the constellation Phoenix and a member of Robert's Quartet.

In other fields

'Eighty-nine' is also:

★ A jersey number of a Russian and NHL hockey legend Alexander Mogilny

★ Part of the name of the baseball team Oklahoma City 89ers (1962-1997)

★ The designation of Interstate 89, a freeway that runs from New Hampshire to Vermont

★ The ISBN Group Identifier for books published in Korea

★ Pop Song 89

★ The year AD '89', 89 BC

★ California Proposition 89, a 2006 California ballot initiative on campaign finance reform

★ The Oklahoma Redhawks were formerly known as the Oklahoma 89ers.

References

1. Weisstein, Eric W. "196-Algorithm." From MathWorld, a Wolfram Web Resource. http://mathworld.wolfram.com/196-Algorithm.html