99
99 is the atomic number of einsteinium, named after Albert Einstein, and the number in a British '99 Flake' ice cream.
- Odd
- Composite
Where 99 fits
Why 99 is special
99 pairs a serious scientific tribute (an element named for Einstein) with a much lighter one: the classic soft-serve cone with a chocolate flake, sold across UK and Irish ice-cream vans.
Same number, different meanings
How 99 is understood across different contexts — never implying one meaning because of another.
- Mathematics
99 pairs a serious scientific tribute (an element named for Einstein) with a much lighter one: the classic soft-serve cone with a chocolate flake, sold across UK and Irish ice-cream vans.
- Science
99 is the atomic number of einsteinium, named after Albert Einstein.
- Culture
A '99 Flake' — a soft-serve ice cream cone with a chocolate flake bar — is a longstanding feature of British and Irish ice-cream vans and seaside shops; the exact origin of its '99' name is debated, but the treat itself is well documented.
99 is part of
Factors & digit properties
- Divisors (6)
- 1, 3, 9, 11, 33, 99
- Prime factorisation
- 3^2 × 11
- Digit sum
- 18
- Digital root
- 9
Representations
- Decimal
- 99
- Binary
- 1100011
- Octal
- 143
- Hexadecimal
- 63
- Roman numeral
- XCIX
- Scientific notation
- 9.900 × 10^1
Other mathematical patterns
- Palindromic number
- Deficient number
- Repdigit
- Kaprekar number
- Lucky number (mathematical sieve)
Related numbers & connections
11 is a factor of 99 (11 × 9 = 99).
View 11 →Science
99 is the atomic number of einsteinium, named after Albert Einstein.
DocumentedScience
Culture
A '99 Flake' — a soft-serve ice cream cone with a chocolate flake bar — is a longstanding feature of British and Irish ice-cream vans and seaside shops; the exact origin of its '99' name is debated, but the treat itself is well documented.
Widely documentedCultureGeography: United Kingdom and Ireland
Common questions
Is 99 a prime number?
No, 99 is not prime.
What are the factors of 99?
The factors of 99 are 1, 3, 9, 11, 33, 99.
What is 99 in Roman numerals?
99 in Roman numerals is XCIX.
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