681
681 is a composite number, odd, a calendar year.
Historical context — 681 AD
Calendar year
Year 681 (DCLXXXI) was a common year starting on Tuesday of the Julian calendar.
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Historical context — 681 BC
Decade
This article concerns the period 689 BC – 680 BC.
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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, 681
- Ended on
-
Saturday
December 31, 681
- Friday the 13ths
-
1
One Friday the 13th this year.
- Decade
-
680s
680–689
- Century
-
7th century
601–700
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,345
1345 years before 2026.
In other calendars
- Hebrew
-
4441 / 4442 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
61 / 62 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
-
1224 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
59 / 60 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
673 / 674 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
603 / 602 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
- 186
- Flips to (rotate 180°)
- 189
- Recamán's sequence
- a(2,262) = 681
- Square (n²)
- 463,761
- Cube (n³)
- 315,821,241
- Divisor count
- 4
- σ(n) — sum of divisors
- 912
- φ(n) — Euler's totient
- 452
- Sum of prime factors
- 230
Primality
Prime factorization: 3 × 227
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- six hundred eighty-one
- Ordinal
- 681st
- Roman numeral
- DCLXXXI
- Binary
- 1010101001
- Octal
- 1251
- Hexadecimal
- 0x2A9
- Base64
- Aqk=
- One's complement
- 64,854 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹 𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- χπαʹ
- Mayan (base 20)
- 𝋡·𝋮·𝋡
- Chinese
- 六百八十一
- Chinese (financial)
- 陸佰捌拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 681 = 7
- e — Euler's number (e)
- Digit 681 = 5
- φ — Golden ratio (φ)
- Digit 681 = 1
- √2 — Pythagoras's (√2)
- Digit 681 = 5
- ln 2 — Natural log of 2
- Digit 681 = 4
- γ — Euler-Mascheroni (γ)
- Digit 681 = 1
Also seen as
UTF-8 encoding: CA A9 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.169.
- Address
- 0.0.2.169
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.2.169
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 681 is an active NANP area code (North American Numbering Plan).
- Primary area
- Statewide
- Region
- West Virginia
- Country
- United States
Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.