684
684 is a composite number, even, a calendar year.
Historical context — 684 AD
Calendar year
Year 684 (DCLXXXIV) was a leap year starting on Friday of the Julian calendar.
Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback Read the full article on Wikipedia →
Historical context — 684 BC
Decade
This article concerns the period 689 BC – 680 BC.
Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback Read the full article on Wikipedia →
Year facts
- Year type
-
Leap year
Divisible by 4 and not by 100; February has 29 days.
- Days in year
- 366
- ISO weeks
- 52
- Started on
-
Tuesday
January 1, 684
- Ended on
-
Wednesday
December 31, 684
- 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
-
1,342
1342 years before 2026.
In other calendars
- Hebrew
-
4444 / 4445 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
64 / 65 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Wood zodiac:Monkey
Sexagenary cycle position 21 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1227 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
62 / 63 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
676 / 677 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
606 / 605 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 2 2 × 3 2 × 19
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- six hundred eighty-four
- Ordinal
- 684th
- Roman numeral
- DCLXXXIV
- Binary
- 1010101100
- Octal
- 1254
- Hexadecimal
- 0x2AC
- Base64
- Aqw=
- One's complement
- 64,851 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹 𒌋𒌋𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺
- Greek (Milesian)
- χπδʹ
- Mayan (base 20)
- 𝋡·𝋮·𝋤
- Chinese
- 六百八十四
- Chinese (financial)
- 陸佰捌拾肆
Digit at this position in famous constants
- π — Pi (π)
- Digit 684 = 5
- e — Euler's number (e)
- Digit 684 = 1
- φ — Golden ratio (φ)
- Digit 684 = 6
- √2 — Pythagoras's (√2)
- Digit 684 = 8
- ln 2 — Natural log of 2
- Digit 684 = 7
- γ — Euler-Mascheroni (γ)
- Digit 684 = 4
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 684, here are decompositions:
- 7 + 677 = 684
- 11 + 673 = 684
- 23 + 661 = 684
- 31 + 653 = 684
- 37 + 647 = 684
- 41 + 643 = 684
- 43 + 641 = 684
- 53 + 631 = 684
Showing the first eight; more decompositions exist.
UTF-8 encoding: CA AC (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.172.
- Address
- 0.0.2.172
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.2.172
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 684 is an active NANP area code (North American Numbering Plan).
- Primary area
- Statewide
- Region
- American Samoa
- 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.