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 connects to:
- fibonacci sequence — belongs to
- 943 — is associated with
Same number, different meanings
How 89 is understood across different contexts — never implying one meaning because of another.
- Mathematics
89 is one of only a handful of numbers that are simultaneously prime and members of the Fibonacci sequence — a genuine mathematical rarity.
- Technology & computing
CWE-89 is SQL injection: input concatenated into a query so it changes the query's structure. Parameterised statements eliminate it entirely, which is why it persists mainly in legacy code.
- Science
89 is the atomic number of actinium, which gives its name to the actinide series. It glows faintly blue in the dark from the intensity of its own radioactivity.
89 is part of
Factors & digit properties
- Divisors (2)
- 1, 89
- Prime factorisation
- 89
- Digit sum
- 17
- Digital root
- 8
Representations
- Decimal
- 89
- Scientific notation
- 8.900 × 10^1
Roman numerals
L X X X I X
LXXXIX uses the subtractive pair IX: one before ten — ten minus one.
Binary
1 0 1 1 0 0 1
1 × 64 + 0 × 32 + 1 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 89
Octal
1 3 1
1 × 64 + 3 × 8 + 1 × 1 = 89
Hexadecimal
5 9
5 × 16 + 9 × 1 = 89
Read as powers of two: 64 + 16 + 8 + 1 = 89.
In historical numeral systems
Egyptian
8 hobbles, 9 strokes
8 × 10 + 9 × 1 = 89. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 vertical wedge (sixties place), 2 corner wedges + 9 vertical wedges (units place)
1 × 60 + 29 = 89. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
pi, then theta, marked as a numeral
pi-theta + keraia
pi + theta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
pe, then tet
pe-tet
pe (80) + tet (9) = 89, written in descending order.
Chinese numerals
bā shí jiǔ
bā shí jiǔ
八 before 十 multiplies it: 8 tens. 九 after it adds 9. The written form mirrors the arithmetic — "bā shí jiǔ". The financial (anti-fraud) form is 捌拾玖.
Maya
4 dots (upper, twenties place) over 1 bar + 4 dots (lower, units place)
4 × 20 + 9 = 89. Places stack vertically with the smallest at the bottom, so the upper group is worth twenty times the lower.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Deficient number
- Sophie Germain prime
Related numbers & connections
89 is the 11th number in the Fibonacci sequence, and is itself prime.
SQL injection is the best known instance of improper neutralisation in a query language.
View 943 →Shares a distinctive class
- belongs toFibonacci sequence
why?
Strength 0.50, confidence "high".
Other connections
- is associated with943
why?
Strength 0.50, confidence "high".
Technology & computing
CWE-89 is SQL injection: input concatenated into a query so it changes the query's structure. Parameterised statements eliminate it entirely, which is why it persists mainly in legacy code.
DocumentedTechnology & computingGeography: International — MITRE CWEPeriod: 2006–
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
Science
89 is the atomic number of actinium, which gives its name to the actinide series. It glows faintly blue in the dark from the intensity of its own radioactivity.
DocumentedScience
Common questions
Is 89 both prime and a Fibonacci number?
Yes — the 11th Fibonacci number, after 55, and prime. Only a handful under 100 are both: 2, 3, 5, 13 and 89. It goes further: 1/89 written out as a decimal has the Fibonacci sequence embedded in it, each term shifted one place right and added.
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. IX is subtractive: one before ten — ten minus one. Written additively it would be LXXXVIIII, which Roman inscriptions used freely — the strict subtractive form is a later convention.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 3 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026