691
+691 is the international calling code for Federated States of Micronesia.
- Odd
- Prime
Where 691 fits
Why 691 is special
Micronesia includes Yap, where large stone discs served as money and ownership was transferred without moving them — a record-keeping system rather than a physical currency.
691 is part of
Factors & digit properties
- Divisors (2)
- 1, 691
- Prime factorisation
- 691
- Digit sum
- 16
- Digital root
- 7
Representations
- Decimal
- 691
- Scientific notation
- 6.910 × 10^2
Roman numerals
D C X C I
DCXCI uses the subtractive pair XC: ten before a hundred — a hundred minus ten.
Binary
1 0 1 0 1 1 0 0 1 1
1 × 512 + 0 × 256 + 1 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 1 × 1 = 691
Octal
1 2 6 3
1 × 512 + 2 × 64 + 6 × 8 + 3 × 1 = 691
Hexadecimal
2 b 3
2 × 256 + b × 16 + 3 × 1 = 691
Read as powers of two: 512 + 128 + 32 + 16 + 2 + 1 = 691.
In historical numeral systems
Egyptian
6 coils of rope, 9 hobbles, 1 stroke
6 × 100 + 9 × 10 + 1 × 1 = 691. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 corner wedge + 1 vertical wedge (sixties place), 3 corner wedges + 1 vertical wedge (units place)
11 × 60 + 31 = 691. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
chi, then koppa, then alpha, marked as a numeral
chi-koppa-alpha + keraia
chi + koppa + alpha written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
tav, then resh, then tsadi, then alef
tav-resh-tsadi-alef
tav (400) + resh (200) + tsadi (90) + alef (1) = 691, written in descending order.
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
Related numbers & connections
Palau and the Federated States of Micronesia are both in free association with the United States. Palau created the world's first shark sanctuary in 2009.
View 680 →Other connections
- is associated with680
why?
Strength 0.50, confidence "high".
Geography
+691 reaches the Federated States of Micronesia. Yap's stone money is frequently cited in discussions of what currency fundamentally is, since transactions changed the record without moving the object.
DocumentedGeographyGeography: Federated States of Micronesia
Common questions
Is 691 a prime number?
Yes, 691 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 691?
The factors of 691 are 1, 691.
What is 691 in Roman numerals?
691 in Roman numerals is DCXCI. XC is subtractive: ten before a hundred — a hundred minus ten. Written additively it would be DCLXXXXI, 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: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 15 July 2026