216
+216 is the international calling code for Tunisia, and ISO 216 is the standard behind A4 paper.
Where 216 fits
Why 216 is special
The two are unrelated and both are widely used. ISO 216 defines the A series so that halving any sheet gives the next size down with the same proportions — a property that requires the ratio to be the square root of two and that no other paper system has.
216 connects to:
- assigned identifiers — appears in
- technical standards bodies — appears in
- 210 — is associated with
Same number, different meanings
How 216 is understood across different contexts — never implying one meaning because of another.
- Mathematics
The two are unrelated and both are widely used. ISO 216 defines the A series so that halving any sheet gives the next size down with the same proportions — a property that requires the ratio to be the square root of two and that no other paper system has.
- Science
216 Kleopatra was resolved by radar as a dog-bone shape with two moons, a configuration attributed to a low-density rubble structure that has been spun and deformed.
- Everyday life
ISO 216 fixes A0 at one square metre with sides in the ratio of the square root of two, so halving any sheet gives the next size down with identical proportions. No other paper system has that property, and it is why enlarging A4 to A3 needs no cropping.
- Geography
+216 reaches Tunisia, completing the 21x North African range with Morocco, Algeria and Libya.
Factors & digit properties
- Divisors (16)
- 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 27, 36, 54, 72, 108, 216
- Prime factorisation
- 2^3 × 3^3
- Digit sum
- 9
- Digital root
- 9
Representations
- Decimal
- 216
- Binary
- 11011000
- Octal
- 330
- Hexadecimal
- d8
- Roman numeral
- CCXVI
- Scientific notation
- 2.160 × 10^2
Other mathematical patterns
- Abundant number
- Powerful number
- Harshad (Niven) number
Related numbers & connections
ISO 216 defines the A-series paper sizes, so the number labels a standard whose content is itself a numbering system.
ISO 216 is the standard that fixes A4 at 210 by 297 mm, by defining A0 as one square metre with sides in the square-root-of-two ratio.
View 210 →Numbers Around Us
- appears inNumbers assigned as identifiers
why?
Strength 0.50, confidence "high".
- appears inStandards issued by an organisation
why?
Strength 0.50, confidence "high".
Other connections
- is associated with210
why?
Strength 0.50, confidence "high".
Science
216 Kleopatra was resolved by radar as a dog-bone shape with two moons, a configuration attributed to a low-density rubble structure that has been spun and deformed.
DocumentedSciencePeriod: 1880–
Everyday life
ISO 216 fixes A0 at one square metre with sides in the ratio of the square root of two, so halving any sheet gives the next size down with identical proportions. No other paper system has that property, and it is why enlarging A4 to A3 needs no cropping.
DocumentedEveryday life
Geography
+216 reaches Tunisia, completing the 21x North African range with Morocco, Algeria and Libya.
DocumentedGeographyGeography: Tunisia
Common questions
Is 216 a prime number?
No, 216 is not prime.
What are the factors of 216?
The factors of 216 are 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 27, 36, 54, 72, 108, 216.
What is 216 in Roman numerals?
216 in Roman numerals is CCXVI.
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: 3 August 2026