861
861 is a composite number, odd, a calendar year.
Historical context — 861 AD
Calendar year
Year 861 (DCCCLXI) was a common year starting on Wednesday of the Julian calendar.
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Historical context — 861 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
-
Saturday
January 1, 861
- Ended on
-
Saturday
December 31, 861
- 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
-
1,165
1165 years before 2026.
In other calendars
- Hebrew
-
4621 / 4622 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
246 / 247 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Metal zodiac:Snake
Sexagenary cycle position 18 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1404 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
239 / 240 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
853 / 854 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
783 / 782 Saka
Indian national calendar; year starts in March.
Properties
- Parity
- Odd
- Digit count
- 3
- Digit sum
- 15
- Digit product
- 48
- Digital root
- 6
- Palindrome
- No
- Bit width
- 10 bits
- Reversed
- 168
- Flips to (rotate 180°)
- 198
- Recamán's sequence
- a(809) = 861
- Square (n²)
- 741,321
- Cube (n³)
- 638,277,381
- Divisor count
- 8
- σ(n) — sum of divisors
- 1,344
- φ(n) — Euler's totient
- 480
- Sum of prime factors
- 51
Primality
Prime factorization: 3 × 7 × 41
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- eight hundred sixty-one
- Ordinal
- 861st
- Roman numeral
- DCCCLXI
- Binary
- 1101011101
- Octal
- 1535
- Hexadecimal
- 0x35D
- Base64
- A10=
- One's complement
- 64,674 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹𒁹𒁹𒁹 𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ωξαʹ
- Mayan (base 20)
- 𝋢·𝋣·𝋡
- Chinese
- 八百六十一
- Chinese (financial)
- 捌佰陸拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 861 = 3
- e — Euler's number (e)
- Digit 861 = 9
- φ — Golden ratio (φ)
- Digit 861 = 5
- √2 — Pythagoras's (√2)
- Digit 861 = 4
- ln 2 — Natural log of 2
- Digit 861 = 3
- γ — Euler-Mascheroni (γ)
- Digit 861 = 7
Also seen as
UTF-8 encoding: CD 9D (2 bytes).
Code page 861 is DOS Icelandic — DOS code page for Icelandic.
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 0.0.3.93.
- Address
- 0.0.3.93
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.3.93
Unspecified address (0.0.0.0/8) — "this network" placeholder.