664
664 is a composite number, even, a calendar year.
Historical context — 664 AD
Calendar year
Year 664 (DCLXIV) was a leap year starting on Monday of the Julian calendar.
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Historical context — 664 BC
Calendar year
The year 664 BC was a year of the pre-Julian Roman calendar.
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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
-
Friday
January 1, 664
- Ended on
-
Saturday
December 31, 664
- Friday the 13ths
-
1
One Friday the 13th this year.
- Decade
-
660s
660–669
- Century
-
7th century
601–700
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,362
1362 years before 2026.
In other calendars
- Hebrew
-
4424 / 4425 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
43 / 44 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Wood zodiac:Rat
Sexagenary cycle position 1 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1207 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
42 / 43 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
656 / 657 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
586 / 585 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 2 3 × 83
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- six hundred sixty-four
- Ordinal
- 664th
- Roman numeral
- DCLXIV
- Binary
- 1010011000
- Octal
- 1230
- Hexadecimal
- 0x298
- Base64
- Apg=
- One's complement
- 64,871 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹 𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺
- Greek (Milesian)
- χξδʹ
- Mayan (base 20)
- 𝋡·𝋭·𝋤
- Chinese
- 六百六十四
- Chinese (financial)
- 陸佰陸拾肆
Digit at this position in famous constants
- π — Pi (π)
- Digit 664 = 4
- e — Euler's number (e)
- Digit 664 = 2
- φ — Golden ratio (φ)
- Digit 664 = 6
- √2 — Pythagoras's (√2)
- Digit 664 = 4
- ln 2 — Natural log of 2
- Digit 664 = 3
- γ — Euler-Mascheroni (γ)
- Digit 664 = 7
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 664, here are decompositions:
- 3 + 661 = 664
- 5 + 659 = 664
- 11 + 653 = 664
- 17 + 647 = 664
- 23 + 641 = 664
- 47 + 617 = 664
- 71 + 593 = 664
- 101 + 563 = 664
Showing the first eight; more decompositions exist.
UTF-8 encoding: CA 98 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.152.
- Address
- 0.0.2.152
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.2.152
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 664 is an active NANP area code (North American Numbering Plan).
- Primary area
- Statewide
- Region
- Montserrat
- Country
- Montserrat
Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.