Number

811

811 is a prime, odd, a calendar year.

811 (eight hundred eleven) is an odd 3-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in Roman numerals it is DCCCXI and in binary, 1100101011.

Arithmetic Number Chen Prime Cube-Free Deficient Number Evil Number Flippable Prime Recamán's Sequence Squarefree Twin Prime Year

Interestingness

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8 notable facts · grade A

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Historical context — 811 AD

Calendar year

Year 811 (DCCCXI) was a common year starting on Wednesday of the Julian calendar, the 811th year of the Common Era (CE) and Anno Domini (AD) designations, the 811th year of the 1st millennium, the 11th year of the 9th century, and the 2nd year of the 810s decade.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Historical context — 811 BC

Decade

This article concerns the period 819 BC – 810 BC.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

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: Saturday
January 1, 811
Ended on: Saturday
December 31, 811
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 810s
810–819
Century: 9th century
801–900
Millennium: 1st millennium
1–1000
Years ago: 1,215
1215 years before 2026.

In other calendars

Hebrew: 4571 / 4572 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 195 / 196 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Rabbit
Sexagenary cycle position 28 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1354 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 189 / 190 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 803 / 804 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 733 / 732 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 10
Digit product: 8
Digital root: 1
Palindrome: No
Bit width: 10 bits
Reversed: 118
Flips to (rotate 180°): 118
Recamán's sequence: a(2,126) = 811
Square (n²): 657,721
Cube (n³): 533,411,731
Divisor count: 2
σ(n) — sum of divisors: 812
φ(n) — Euler's totient: 810

Primality

811 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 811

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 811)

1 × 811

First multiples

811 · 1,622 (double) · 2,433 · 3,244 · 4,055 · 4,866 · 5,677 · 6,488 · 7,299 · 8,110

Sums & aliquot sequence

As consecutive integers: 405 + 406

Continued fraction of √n

√811 = [28; (2, 10, 1, 8, 1, 1, 2, 1, 1, 1, 3, 6, 18, 1, 4, 1, 2, 1, 27, 1, 2, 1, 4, 1, …)]

Period length 38 — the block in parentheses repeats forever.

Representations

In words: eight hundred eleven
Ordinal: 811th
Roman numeral: DCCCXI
Binary: 1100101011
Octal: 1453
Hexadecimal: 0x32B
Base64: Ays=
One's complement: 64,724 (16-bit)
Scientific notation: 8.11 × 10²
As a duration: 811 s = 13 minutes, 31 seconds

In other bases

ternary (3) 1010001

quaternary (4) 30223

quinary (5) 11221

senary (6) 3431

septenary (7) 2236

nonary (9) 1101

undecimal (11) 678

duodecimal (12) 577

tridecimal (13) 4a5

tetradecimal (14) 41d

pentadecimal (15) 391

As an angle

811° = 2 × 360° + 91°

91° ≈ 1.588 rad

Compass bearing: E (east)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹𒁹𒁹 𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓏺
Greek (Milesian): ωιαʹ
Mayan (base 20): 𝋢·𝋠·𝋫
Chinese: 八百一十一
Chinese (financial): 捌佰壹拾壹

In other modern scripts

Eastern Arabic ٨١١ Devanagari ८११ Bengali ৮১১ Tamil ௮௧௧ Thai ๘๑๑ Tibetan ༨༡༡ Khmer ៨១១ Lao ໘໑໑ Burmese ၈၁၁

Digit at this position in famous constants

π — Pi (π): Digit 811 = 5
e — Euler's number (e): Digit 811 = 3
φ — Golden ratio (φ): Digit 811 = 7
√2 — Pythagoras's (√2): Digit 811 = 2
ln 2 — Natural log of 2: Digit 811 = 3
γ — Euler-Mascheroni (γ): Digit 811 = 5

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 809 (gap of 2)
Next prime: 821 (gap of 10)

Pair status: twin with 809.

Unicode codepoint

Combining Inverted Double Arch Below

U+032B

Non-spacing mark (Mn)

UTF-8 encoding: CC AB (2 bytes).

Lookup U+032B on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#00032B

RGB(0, 3, 43)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.3.43.

Address: 0.0.3.43
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.3.43

Unspecified address (0.0.0.0/8) — "this network" placeholder.

Musical pitch

Heard as a frequency, 811 Hz is closest to:

Concert pitch (A4 = 440 Hz): G♯5 (830.6 Hz, -41¢)
Scientific pitch (C4 = 256 Hz): G♯5 (812.7 Hz, -4¢)
Baroque pitch (A4 = 415 Hz): A5 (830 Hz, -40¢)