99
A "99" is a soft-serve cone with a chocolate flake, standard in British and Irish ice-cream vans since the 1930s, and nobody knows why it is called that. 99 is the atomic number of einsteinium.
- 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
Technetium-99m is used in the large majority of diagnostic nuclear medicine procedures. Its six-hour half-life means it cannot be stockpiled, so supply depends on a small number of ageing reactors.
- 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.
- Sport
Dismissal on 99 in cricket carries a significance that 98 does not, solely because 100 is a round number in decimal. The pressure is real and its cause is notational.
- Finance & economics
Prices ending in 99 are the most studied pattern in retail pricing. The usual explanation is left-digit bias — £9.99 is read as 'nine something' rather than rounded to ten — and controlled studies do find measurable effects, though smaller and less reliable than the practice's ubiquity suggests. A separate historical account holds that the odd price forced a cashier to open the till and record the sale, making theft harder; that story is often repeated and poorly evidenced.
- Religion & belief
In Islam, God is described by ninety-nine names, al-asma al-husna, which are recited and used in devotion. Attested in hadith collections from the ninth century onward. The count is traditional and the list is not fixed: the enumerations given by al-Tirmidhi and by Ibn Majah differ from each other, and neither is in the Qur'an as a list. A prayer bead string, the misbaha, has thirty-three beads and is told three times.
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
- Scientific notation
- 9.900 × 10^1
Roman numerals
X C I X
XCIX uses the subtractive pair IX: one before ten — ten minus one.
Binary
1 1 0 0 0 1 1
1 × 64 + 1 × 32 + 0 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 1 × 1 = 99
Octal
1 4 3
1 × 64 + 4 × 8 + 3 × 1 = 99
Hexadecimal
6 3
6 × 16 + 3 × 1 = 99
Read as powers of two: 64 + 32 + 2 + 1 = 99.
In historical numeral systems
Egyptian
9 hobbles, 9 strokes
9 × 10 + 9 × 1 = 99. 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), 3 corner wedges + 9 vertical wedges (units place)
1 × 60 + 39 = 99. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
koppa, then theta, marked as a numeral
koppa-theta + keraia
koppa + theta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
tsadi, then tet
tsadi-tet
tsadi (90) + tet (9) = 99, written in descending order.
Chinese numerals
jiǔ shí jiǔ
jiǔ shí jiǔ
九 before 十 multiplies it: 9 tens. 九 after it adds 9. The written form mirrors the arithmetic — "jiǔ shí jiǔ". The financial (anti-fraud) form is 玖拾玖.
Maya
4 dots (upper, twenties place) over 3 bars + 4 dots (lower, units place)
4 × 20 + 19 = 99. 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
- Palindromic number
- Deficient number
- Repdigit
- Kaprekar number
- Lucky number (mathematical sieve)
Related numbers & connections
33 is a factor of 99 (33 × 3 = 99).
View 33 →99 appears in Numbers in culture and belief, the topic covering numbers that carry a documented cultural fact.
Science
Technetium-99m is used in the large majority of diagnostic nuclear medicine procedures. Its six-hour half-life means it cannot be stockpiled, so supply depends on a small number of ageing reactors.
DocumentedScienceGeography: GlobalPeriod: 1938–Einsteinium was detected in debris from the 1952 Ivy Mike test and kept secret until 1955. Naming it after a physicist who had campaigned against nuclear weapons was not his choice.
DocumentedSciencePeriod: 195299 is the atomic number of einsteinium, first identified in the fallout of a 1952 thermonuclear test and named for Albert Einstein. It has never been produced in weighable amounts.
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
Sport
Dismissal on 99 in cricket carries a significance that 98 does not, solely because 100 is a round number in decimal. The pressure is real and its cause is notational.
DocumentedSportGeography: Cricket-playing nations
Finance & economics
Prices ending in 99 are the most studied pattern in retail pricing. The usual explanation is left-digit bias — £9.99 is read as 'nine something' rather than rounded to ten — and controlled studies do find measurable effects, though smaller and less reliable than the practice's ubiquity suggests. A separate historical account holds that the odd price forced a cashier to open the till and record the sale, making theft harder; that story is often repeated and poorly evidenced.
DocumentedFinance & economics
Religion & belief
In Islam, God is described by ninety-nine names, al-asma al-husna, which are recited and used in devotion. Attested in hadith collections from the ninth century onward. The count is traditional and the list is not fixed: the enumerations given by al-Tirmidhi and by Ibn Majah differ from each other, and neither is in the Qur'an as a list. A prayer bead string, the misbaha, has thirty-three beads and is told three times.
Tradition / practiceReligion & beliefCulture: IslamPresented as belief or tradition, not as an established fact.
Common questions
Why is it called a 99 Flake?
Nobody knows. Cadbury's own account has cited an Italian ice-cream family and the Italian king's guard of ninety-nine, and the company has acknowledged the origin is not documented. What is documented is the product: a soft-serve cone with a Flake pushed into it, standard in British and Irish ice-cream vans since the 1930s.
Why do prices end in 99?
Mostly left-digit bias: £9.99 is read as 'nine something' rather than rounded up to ten. Controlled studies do find an effect, though a smaller and less consistent one than the practice's ubiquity suggests. A rival explanation — that an odd price forced the cashier to open the till and record the sale — is often repeated and poorly evidenced.
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. IX is subtractive: one before ten — ten minus one. Written additively it would be LXXXXVIIII, 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: 7 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026