Number reference
89 explained.
89: eighty-nine, prime, fibonacci number; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- eighty-nine
- Classification
- prime
- Factors
- 1, 89
- Prime factorization
- 89
- Square root
- 9.433981
- Cube root
- 4.464745
- Binary
- 1011001
- Octal
- 131
- Hexadecimal
- 59
- Roman numeral
- LXXXIX
- Digit sum
- 17
- Digital root
- 8
What makes 89 notable
- Prime. 89 is prime: it has exactly two divisors, 1 and itself, so it cannot be split into equal whole-number groups any other way.
- Fibonacci number. 89 appears in the Fibonacci sequence, where each term is the sum of the two before it.
89 in everyday use
Eighty-nine is the atomic number of actinium, the radioactive metal that gives the actinide series its name. The Berlin Wall fell in 1989, the same year Tim Berners-Lee proposed the World Wide Web. In the Fibonacci sequence 89 follows 55, and it hides a curiosity: the decimal expansion of 1/89 — 0.01123595505… — is what you get by adding the Fibonacci numbers shifted one decimal place further each time.
Eighty-nine is the 24th prime and the eleventh Fibonacci number, 34 + 55. It is the sum of two squares, 64 + 25, the squares of the Fibonacci numbers 8 and 5. It is a Sophie Germain prime, because 2 × 89 + 1 = 179 is also prime. Its reversal, 98, is 2 × 49, so it is not an emirp. In binary it is 1011001.
Nearby numbers
How to read this page
Because 89 is prime, the factor list stops at 1 and 89 itself, so it cannot be shared into equal whole-number groups. That is also what makes it useful as a building block: every larger number with 89 in its prime factorisation inherits it from here.
Percentage calculator · Fraction calculator · Browse Number Explorer