866
866 is a composite number, even, a calendar year.
Historical context — 866 AD
Calendar year
Year 866 (DCCCLXVI) was a common year starting on Tuesday of the Julian calendar.
Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback Read the full article on Wikipedia →
Historical context — 866 BC
Decade
This article concerns the period 869 BC – 860 BC.
Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback Read the full article on Wikipedia →
Year facts
- Year type
-
Common year
Standard 365-day year; not divisible by 4 (or divisible by 100 but not 400).
- Days in year
- 365
- ISO weeks
- 52
- Started on
-
Friday
January 1, 866
- Ended on
-
Friday
December 31, 866
- Friday the 13ths
-
1
One Friday the 13th this year.
- Decade
-
860s
860–869
- Century
-
9th century
801–900
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,160
1160 years before 2026.
In other calendars
- Hebrew
-
4626 / 4627 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
251 / 252 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Fire zodiac:Dog
Sexagenary cycle position 23 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1409 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
244 / 245 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
858 / 859 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
788 / 787 Saka
Indian national calendar; year starts in March.
Properties
- Parity
- Even
- Digit count
- 3
- Digit sum
- 20
- Digit product
- 288
- Digital root
- 2
- Palindrome
- No
- Bit width
- 10 bits
- Reversed
- 668
- Flips to (rotate 180°)
- 998
- Recamán's sequence
- a(799) = 866
- Square (n²)
- 749,956
- Cube (n³)
- 649,461,896
- Divisor count
- 4
- σ(n) — sum of divisors
- 1,302
- φ(n) — Euler's totient
- 432
- Sum of prime factors
- 435
Primality
Prime factorization: 2 × 433
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- eight hundred sixty-six
- Ordinal
- 866th
- Roman numeral
- DCCCLXVI
- Binary
- 1101100010
- Octal
- 1542
- Hexadecimal
- 0x362
- Base64
- A2I=
- One's complement
- 64,669 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹𒁹𒁹𒁹 𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- ωξϛʹ
- Mayan (base 20)
- 𝋢·𝋣·𝋦
- Chinese
- 八百六十六
- Chinese (financial)
- 捌佰陸拾陸
Digit at this position in famous constants
- π — Pi (π)
- Digit 866 = 7
- e — Euler's number (e)
- Digit 866 = 7
- φ — Golden ratio (φ)
- Digit 866 = 2
- √2 — Pythagoras's (√2)
- Digit 866 = 0
- ln 2 — Natural log of 2
- Digit 866 = 7
- γ — Euler-Mascheroni (γ)
- Digit 866 = 0
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 866, here are decompositions:
- 3 + 863 = 866
- 7 + 859 = 866
- 13 + 853 = 866
- 37 + 829 = 866
- 43 + 823 = 866
- 79 + 787 = 866
- 97 + 769 = 866
- 109 + 757 = 866
Showing the first eight; more decompositions exist.
UTF-8 encoding: CD A2 (2 bytes).
Code page 866 is DOS Russian — DOS code page for Russian Cyrillic.
Code pages are integer identifiers used by Windows and other systems to refer to specific character encodings.
As an unsigned 32-bit integer, this is the IPv4 address 0.0.3.98.
- Address
- 0.0.3.98
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.3.98
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 866 is an active NANP area code (North American Numbering Plan).
- Primary area
- Toll-free
- Region
- (special)
- Country
- North America
Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.