Number

809

809 is a prime, odd, a calendar year.

809 (eight hundred nine) 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 DCCCIX and in binary, 1100101001.

Arithmetic Number Chen Prime Cube-Free Deficient Number Flippable Odious Number Pernicious Number Prime Pythagorean Prime Recamán's Sequence Sophie Germain Prime Squarefree Twin Prime Year

Interestingness

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Historical context — 809 AD

Calendar year

Year 809 (DCCCIX) was a common year starting on Monday of the Julian calendar, the 809th year of the Common Era (CE) and Anno Domini (AD) designations, the 809th year of the 1st millennium, the 9th year of the 9th century, and the 10th and last year of the 800s decade.

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

Historical context — 809 BC

Decade

This article concerns the period 809 BC – 800 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: 53
Long year: contains 53 ISO weeks.
Started on: Thursday
January 1, 809
Ended on: Thursday
December 31, 809
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 800s
800–809
Century: 9th century
801–900
Millennium: 1st millennium
1–1000
Years ago: 1,217
1217 years before 2026.

In other calendars

Hebrew: 4569 / 4570 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 193 / 194 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Earth zodiac:Ox
Sexagenary cycle position 26 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1352 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 187 / 188 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 801 / 802 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 731 / 730 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 17
Digit product: 0
Digital root: 8
Palindrome: No
Bit width: 10 bits
Reversed: 908
Flips to (rotate 180°): 608
Recamán's sequence: a(2,130) = 809
Square (n²): 654,481
Cube (n³): 529,475,129
Divisor count: 2
σ(n) — sum of divisors: 810
φ(n) — Euler's totient: 808

Primality

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

Divisors & multiples

All divisors (2)

1 · 809

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 809)

1 × 809

First multiples

809 · 1,618 (double) · 2,427 · 3,236 · 4,045 · 4,854 · 5,663 · 6,472 · 7,281 · 8,090

Sums & aliquot sequence

As a sum of two squares: 5² + 28²

As consecutive integers: 404 + 405

Continued fraction of √n

√809 = [28; (2, 3, 1, 7, 2, 1, 6, 2, 3, 11, 11, 3, 2, 6, 1, 2, 7, 1, 3, 2, 56)]

Period length 21 — the block in parentheses repeats forever.

Representations

In words: eight hundred nine
Ordinal: 809th
Roman numeral: DCCCIX
Binary: 1100101001
Octal: 1451
Hexadecimal: 0x329
Base64: Ayk=
One's complement: 64,726 (16-bit)
Scientific notation: 8.09 × 10²
As a duration: 809 s = 13 minutes, 29 seconds

In other bases

ternary (3) 1002222

quaternary (4) 30221

quinary (5) 11214

senary (6) 3425

septenary (7) 2234

nonary (9) 1088

undecimal (11) 676

duodecimal (12) 575

tridecimal (13) 4a3

tetradecimal (14) 41b

pentadecimal (15) 38e

Palindromic in base 11, base 12

As an angle

809° = 2 × 360° + 89°

89° ≈ 1.553 rad

Compass bearing: E (east)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹𒁹𒁹 𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ωθʹ
Mayan (base 20): 𝋢·𝋠·𝋩
Chinese: 八百零九
Chinese (financial): 捌佰零玖

In other modern scripts

Eastern Arabic ٨٠٩ Devanagari ८०९ Bengali ৮০৯ Tamil ௮௦௯ Thai ๘๐๙ Tibetan ༨༠༩ Khmer ៨០៩ Lao ໘໐໙ Burmese ၈၀၉

Digit at this position in famous constants

π — Pi (π): Digit 809 = 4
e — Euler's number (e): Digit 809 = 2
φ — Golden ratio (φ): Digit 809 = 9
√2 — Pythagoras's (√2): Digit 809 = 0
ln 2 — Natural log of 2: Digit 809 = 2
γ — Euler-Mascheroni (γ): Digit 809 = 1

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 797 (gap of 12)
Next prime: 811 (gap of 2)

Pair status: twin with 811.

Unicode codepoint

Combining Vertical Line Below

U+0329

Non-spacing mark (Mn)

UTF-8 encoding: CC A9 (2 bytes).

Lookup U+0329 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000329

RGB(0, 3, 41)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.3.41.

Address: 0.0.3.41
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.3.41

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

NANP area code 809

The number 809 is an active NANP area code (North American Numbering Plan).

Primary area: Statewide
Region: Dominican Republic
Country: Dominican Republic

Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.

Look up area code 809 ↗

Musical pitch

Heard as a frequency, 809 Hz is closest to:

Concert pitch (A4 = 440 Hz): G♯5 (830.6 Hz, -46¢ — about midway to G5)
Scientific pitch (C4 = 256 Hz): G♯5 (812.7 Hz, -8¢)
Baroque pitch (A4 = 415 Hz): A5 (830 Hz, -44¢)