639
639 is a composite number, odd, a calendar year.
Historical context — 639 AD
Calendar year
Year 639 (DCXXXIX) was a common year starting on Friday of the Julian calendar.
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Historical context — 639 BC
Calendar year
The year 639 BC was a year of the pre-Julian Roman calendar.
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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
-
Tuesday
January 1, 639
- Ended on
-
Tuesday
December 31, 639
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Decade
-
630s
630–639
- Century
-
7th century
601–700
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,387
1387 years before 2026.
In other calendars
- Hebrew
-
4399 / 4400 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
17 / 18 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Earth zodiac:Pig
Sexagenary cycle position 36 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1182 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
17 / 18 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
631 / 632 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
561 / 560 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 3 2 × 71
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- six hundred thirty-nine
- Ordinal
- 639th
- Roman numeral
- DCXXXIX
- Binary
- 1001111111
- Octal
- 1177
- Hexadecimal
- 0x27F
- Base64
- An8=
- One's complement
- 64,896 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋 𒌋𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- χλθʹ
- Mayan (base 20)
- 𝋡·𝋫·𝋳
- Chinese
- 六百三十九
- Chinese (financial)
- 陸佰參拾玖
Digit at this position in famous constants
- π — Pi (π)
- Digit 639 = 0
- e — Euler's number (e)
- Digit 639 = 8
- φ — Golden ratio (φ)
- Digit 639 = 4
- √2 — Pythagoras's (√2)
- Digit 639 = 8
- ln 2 — Natural log of 2
- Digit 639 = 7
- γ — Euler-Mascheroni (γ)
- Digit 639 = 2
Also seen as
UTF-8 encoding: C9 BF (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.127.
- Address
- 0.0.2.127
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.2.127
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 639 is an active NANP area code (North American Numbering Plan).
- Primary area
- Statewide
- Region
- Saskatchewan
- Country
- Canada
Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.