1,280
1,280 is a composite number, even, a calendar year.
Historical context — 1280 AD
Calendar year
1280 (MCCLXXX) was a leap year starting on Monday in the Julian 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
-
Monday
January 1, 1280
- Ended on
-
Tuesday
December 31, 1280
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Decade
-
1280s
1280–1289
- Century
-
13th century
1201–1300
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
746
746 years before 2026.
In other calendars
- Hebrew
-
5040 / 5041 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
678 / 679 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Metal zodiac:Dragon
Sexagenary cycle position 17 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
1823 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
658 / 659 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1272 / 1273 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1202 / 1201 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 2 8 × 5
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- one thousand two hundred eighty
- Ordinal
- 1280th
- Roman numeral
- MCCLXXX
- Binary
- 10100000000
- Octal
- 2400
- Hexadecimal
- 0x500
- Base64
- BQA=
- One's complement
- 64,255 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒁹 𒌋𒌋
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆
- Greek (Milesian)
- ͵ασπʹ
- Mayan (base 20)
- 𝋣·𝋤·𝋠
- Chinese
- 一千二百八十
- Chinese (financial)
- 壹仟貳佰捌拾
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,280 = 6
- e — Euler's number (e)
- Digit 1,280 = 7
- φ — Golden ratio (φ)
- Digit 1,280 = 7
- √2 — Pythagoras's (√2)
- Digit 1,280 = 6
- ln 2 — Natural log of 2
- Digit 1,280 = 4
- γ — Euler-Mascheroni (γ)
- Digit 1,280 = 8
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 1280, here are decompositions:
- 3 + 1277 = 1280
- 31 + 1249 = 1280
- 43 + 1237 = 1280
- 67 + 1213 = 1280
- 79 + 1201 = 1280
- 109 + 1171 = 1280
- 127 + 1153 = 1280
- 151 + 1129 = 1280
Showing the first eight; more decompositions exist.
UTF-8 encoding: D4 80 (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.5.0.
- Address
- 0.0.5.0
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.5.0
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The digit sequence 1280 first appears in π at position 6,281 of the decimal expansion (the 6,281ordinal-suffix:st digit after the integer 3).
Search range: the first 1,000,000 fractional digits of π. Any 6-digit-or-shorter string is virtually guaranteed to appear in there — the more interesting signal is the position.