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
- Scientific notation
- 2.160 × 10^2
Roman numerals
C C X V I
Binary
1 1 0 1 1 0 0 0
1 × 128 + 1 × 64 + 0 × 32 + 1 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 0 × 1 = 216
Octal
3 3 0
3 × 64 + 3 × 8 + 0 × 1 = 216
Hexadecimal
d 8
d × 16 + 8 × 1 = 216
Read as powers of two: 128 + 64 + 16 + 8 = 216.
In historical numeral systems
Egyptian
2 coils of rope, 1 hobble, 6 strokes
2 × 100 + 1 × 10 + 6 × 1 = 216. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 vertical wedges (sixties place), 3 corner wedges + 6 vertical wedges (units place)
3 × 60 + 36 = 216. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
sigma, then iota, then stigma, marked as a numeral
sigma-iota-stigma + keraia
sigma + iota + stigma written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
resh, then tet, then zayin
resh-tet-zayin
The ordinary rule would give יו (yod 10 + vav 6), also a divine-name form, so 16 is written טז — tet (9) + zayin (7).
Maya
2 bars (upper, twenties place) over 3 bars + 1 dot (lower, units place)
10 × 20 + 16 = 216. 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
- 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: 15 July 2026