← 88 89 90 →
Cardinaleighty-nine
Ordinal89th
(eighty-ninth)
Factorizationprime
Prime24th
Divisors1, 89
Greek numeralΠΘ´
Roman numeralLXXXIX
Binary10110012
Ternary100223
Senary2256
Octal1318
Duodecimal7512

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

## In mathematics

89 is:

${\displaystyle {\frac {1}{89))=\sum _{n=1}^{\infty }{F(n)\times 10^{-(n+1)))=0.011235955\dots \ .}$
• a Markov number, appearing in solutions to the Markov Diophantine equation with other odd-indexed Fibonacci numbers.

M89 is the 10th Mersenne prime.

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: 8813200023188.[4]

There are exactly 1000 prime numbers between 1 and 892=7921. [5]

Eighty-nine is:

## In other fields

Eighty-nine is also: