660
660 is a composite number, even, a calendar year.
Historical context — 660 AD
Calendar year
Year 660 (DCLX) was a leap year starting on Wednesday of the Julian calendar.
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Historical context — 660 BC
Calendar year
The year 660 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
-
Sunday
January 1, 660
- Ended on
-
Monday
December 31, 660
- Friday the 13ths
-
3
3 Friday the 13ths this year.
- Decade
-
660s
660–669
- Century
-
7th century
601–700
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,366
1366 years before 2026.
In other calendars
- Hebrew
-
4420 / 4421 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
39 / 40 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Metal zodiac:Monkey
Sexagenary cycle position 57 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1203 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
38 / 39 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
652 / 653 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
582 / 581 Saka
Indian national calendar; year starts in March.
Properties
- Parity
- Even
- Digit count
- 3
- Digit sum
- 12
- Digit product
- 0
- Digital root
- 3
- Palindrome
- No
- Bit width
- 10 bits
- Reversed
- 66
- Flips to (rotate 180°)
- 99
- Recamán's sequence
- a(2,304) = 660
- Square (n²)
- 435,600
- Cube (n³)
- 287,496,000
- Divisor count
- 24
- σ(n) — sum of divisors
- 2,016
- φ(n) — Euler's totient
- 160
- Sum of prime factors
- 23
Primality
Prime factorization: 2 2 × 3 × 5 × 11
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- six hundred sixty
- Ordinal
- 660th
- Roman numeral
- DCLX
- Binary
- 1010010100
- Octal
- 1224
- Hexadecimal
- 0x294
- Base64
- ApQ=
- One's complement
- 64,875 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹 ·
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆
- Greek (Milesian)
- χξʹ
- Mayan (base 20)
- 𝋡·𝋭·𝋠
- Chinese
- 六百六十
- Chinese (financial)
- 陸佰陸拾
Digit at this position in famous constants
- π — Pi (π)
- Digit 660 = 0
- e — Euler's number (e)
- Digit 660 = 2
- φ — Golden ratio (φ)
- Digit 660 = 1
- √2 — Pythagoras's (√2)
- Digit 660 = 3
- ln 2 — Natural log of 2
- Digit 660 = 2
- γ — Euler-Mascheroni (γ)
- Digit 660 = 5
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 660, here are decompositions:
- 7 + 653 = 660
- 13 + 647 = 660
- 17 + 643 = 660
- 19 + 641 = 660
- 29 + 631 = 660
- 41 + 619 = 660
- 43 + 617 = 660
- 47 + 613 = 660
Showing the first eight; more decompositions exist.
UTF-8 encoding: CA 94 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.148.
- Address
- 0.0.2.148
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.2.148
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 660 is an active NANP area code (North American Numbering Plan).
- Primary area
- Sedalia / Marshall
- Region
- Missouri
- 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.
This passes the ABA routing number checksum and matches the Federal Reserve numbering scheme.
Banks operate many routing numbers per state and division; an unmatched checksum-valid number can still be a real RTN at a smaller institution.