685
+685 is the international calling code for Samoa.
- Odd
- Composite
Where 685 fits
Why 685 is special
Samoa skipped 30 December 2011 entirely, moving across the international date line to align its working week with Australia and New Zealand.
Factors & digit properties
- Divisors (4)
- 1, 5, 137, 685
- Prime factorisation
- 5 × 137
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 685
- Binary
- 1010101101
- Octal
- 1255
- Hexadecimal
- 2ad
- Roman numeral
- DCLXXXV
- Scientific notation
- 6.850 × 10^2
Other mathematical patterns
- Deficient number
- Semiprime
- Lucky number (mathematical sieve)
Related numbers & connections
Tonga and Samoa are Polynesian neighbours. Tonga was never colonised, and Samoa deleted a whole calendar day in 2011 to change sides of the date line.
View 676 →Geography
+685 reaches Samoa, which deleted a whole calendar day in 2011 to switch sides of the date line. The change aligned its business week with its main trading partners.
DocumentedGeographyGeography: Samoa
Common questions
Is 685 a prime number?
No, 685 is not prime.
What are the factors of 685?
The factors of 685 are 1, 5, 137, 685.
What is 685 in Roman numerals?
685 in Roman numerals is DCLXXXV.
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: 3 August 2026