# 89 (number)

 ← 88 89 90 →
Cardinal eighty-nine
Ordinal 89th
(eighty-ninth)
Factorization prime
Prime 24th
Divisors 1, 89
Greek numeral ΠΘ´
Roman numeral LXXXIX
Binary 10110012
Ternary 100223
Quaternary 11214
Quinary 3245
Senary 2256
Octal 1318
Duodecimal 7512
Vigesimal 4920
Base 36 2H36

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.[4]

Eighty-nine is:

## In other fields

Eighty-nine is also: