89 (number)

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

← 88 90 → 89
← 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-nine
Ordinal	89th (eighty-ninth)
Numeral system	89
Factorization	89
Prime	24th
Divisors	1, 89
Roman numeral	LXXXIX
Binary	10110012
Octal	1318
Duodecimal	7512
Hexadecimal	5916

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. The first few digits of its reciprocal coincide with the Fibonacci sequence due to the identity

$\frac{1}{89}=\sum_{n=1}^\infty{F(n)\times 10^{-(n+1)}}=0.011235955\dots\ .$

89 is also a Markov number, appearing in solutions to the Markov Diophantine equation with other odd-indexed Fibonacci numbers.

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.

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

TI-89

Eighty-nine is also:

• 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 designation of U.S. Route 89, a north-south highway that runs from Montana to Arizona
• 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.
• In Rugby, an "89" or eight-nine move is a phase following a scrum, in which the number 8 catches the ball and transfers it to number 9 (scrum half).
• The greatest number of verses in a chapter of a book of the Bible other than the Book of Psalms—specifically Numbers chapter 7.
• The number of units of each colour in the board game Blokus
• The number of the French department Yonne
• Information Is Beautiful cites eighty-nine as one of the words censored on the Chinese Internet.

See also

• Hellin's law