Number

1,280

1,280 is a composite number, even, a calendar year.

1,280 (one thousand two hundred eighty) is an even 4-digit number. It is a composite number with 18 divisors, and factors as 2⁸ × 5. Its proper divisors sum to 1,786, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is MCCLXXX and in binary, 10100000000.

Abundant Number Evil Number Frugal Number Gapful Number Pernicious Number Practical Number Recamán's Sequence Semiperfect Number Year

Interestingness

★ ★ ★ ☆ ☆

5 notable facts · grade C

1,268 1,269 1,270 1,271 1,272 1,273 1,274 1,275 1,276 1,277 1,278 1,279 1,280 1,281 1,282 1,283 1,284 1,285 1,286 1,287 1,288 1,289 1,290 1,291 1,292

less more

Historical context — 1280 AD

Calendar year

1280 (MCCLXXX) was a leap year starting on Monday in the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 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: 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

Parity: Even
Digit count: 4
Digit sum: 11
Digit product: 0
Digital root: 2
Palindrome: No
Bit width: 11 bits
Reversed: 821
Recamán's sequence: a(30,488) = 1,280
Square (n²): 1,638,400
Cube (n³): 2,097,152,000
Divisor count: 18
σ(n) — sum of divisors: 3,066
φ(n) — Euler's totient: 512
Sum of prime factors: 21

Primality

Prime factorization: 2 ⁸ × 5

Nearest primes: 1,279 (−1) · 1,283 (+3)

Divisors & multiples

All divisors (18)

1 · 2 · 4 · 5 · 8 · 10 · 16 · 20 · 32 · 40 · 64 · 80 · 128 · 160 · 256 · 320 · 640 (half) · 1280

Aliquot sum (sum of proper divisors): 1,786

Factor pairs (a × b = 1,280)

1 × 1280

2 × 640

4 × 320

5 × 256

8 × 160

10 × 128

16 × 80

20 × 64

32 × 40

First multiples

1,280 · 2,560 (double) · 3,840 · 5,120 · 6,400 · 7,680 · 8,960 · 10,240 · 11,520 · 12,800

Sums & aliquot sequence

As a sum of two squares: 16² + 32²

As consecutive integers: 254 + 255 + 256 + 257 + 258

Aliquot sequence: 1,280 → 1,786 → 1,094 → 550 → 566 → 286 → 218 → 112 → 136 → 134 → 70 → 74 → 40 → 50 → 43 → 1 → 0 — terminates at zero

Continued fraction of √n

√1,280 = [35; (1, 3, 2, 17, 2, 3, 1, 70)]

Period length 8 — the block in parentheses repeats forever.

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)
Scientific notation: 1.28 × 10³
As a duration: 1,280 s = 21 minutes, 20 seconds

In other bases

ternary (3) 1202102

quaternary (4) 110000

quinary (5) 20110

senary (6) 5532

septenary (7) 3506

nonary (9) 1672

undecimal (11) a64

duodecimal (12) 8a8

tridecimal (13) 776

tetradecimal (14) 676

pentadecimal (15) 5a5

Palindromic in base 12, base 14, base 15

As an angle

1,280° = 3 × 360° + 200°

200° ≈ 3.491 rad

Compass bearing: SSW (south-southwest)

Why does a circle have 360 degrees? →

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

In other modern scripts

Eastern Arabic ١٢٨٠ Devanagari १२८० Bengali ১২৮০ Tamil ௧௨௮௦ Thai ๑๒๘๐ Tibetan ༡༢༨༠ Khmer ១២៨០ Lao ໑໒໘໐ Burmese ၁၂၈၀

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 decomposition

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.

Unicode codepoint

Cyrillic Capital Letter Komi De

U+0500

Uppercase letter (Lu)

UTF-8 encoding: D4 80 (2 bytes).

Lookup U+0500 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000500

RGB(0, 5, 0)

IPv4 address

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.

Musical pitch

Heard as a frequency, 1,280 Hz is closest to:

Concert pitch (A4 = 440 Hz): D♯6 (1244.5 Hz, +49¢ — about midway to E6)
Scientific pitch (C4 = 256 Hz): E6 (1290.2 Hz, -14¢)
Baroque pitch (A4 = 415 Hz): E6 (1243.6 Hz, +50¢ — about midway to F6)

Position in π

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.

Look up 1280 on Pi Search ↗