89
89 is both prime and the 11th Fibonacci number, and the atomic number of actinium.
Where 89 fits
Why 89 is special
89 is one of only a handful of numbers that are simultaneously prime and members of the Fibonacci sequence — a genuine mathematical rarity.
89 is part of
Factors & digit properties
- Divisors (2)
- 1, 89
- Prime factorisation
- 89
- Digit sum
- 17
- Digital root
- 8
Representations
- Decimal
- 89
- Binary
- 1011001
- Octal
- 131
- Hexadecimal
- 59
- Roman numeral
- LXXXIX
- Scientific notation
- 8.900 × 10^1
Other mathematical patterns
- Deficient number
- Sophie Germain prime
Related numbers & connections
89 is the 11th number in the Fibonacci sequence, and is itself prime.
Shares a distinctive class
- belongs toFibonacci sequence
why?
Strength 0.50, confidence "high".
Science
89 is the atomic number of actinium, the element that gives its name to the wider actinide series.
DocumentedScience
Mathematics
89 is both prime and the 11th Fibonacci number (…, 34, 55, 89) — one of only a handful of numbers that are simultaneously prime and Fibonacci.
DocumentedMathematics
Common questions
Is 89 a prime number?
Yes, 89 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 89?
The factors of 89 are 1, 89.
What is 89 in Roman numerals?
89 in Roman numerals is LXXXIX.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026