Number

1,811

1,811 is a prime, odd, a calendar year.

1,811 (one thousand eight hundred eleven) is an odd 4-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in Roman numerals it is MDCCCXI and in binary, 11100010011.

Arithmetic Number Cube-Free Deficient Number Emirp Evil Number Flippable Prime Recamán's Sequence Sophie Germain Prime Squarefree Year

Interestingness

★ ★ ★ ★ ★

8 notable facts · grade A

1,799 1,800 1,801 1,802 1,803 1,804 1,805 1,806 1,807 1,808 1,809 1,810 1,811 1,812 1,813 1,814 1,815 1,816 1,817 1,818 1,819 1,820 1,821 1,822 1,823

less more

Notable events — 1811 AD

Mar 11 British weavers riot in the early Luddite protests.
Nov 7 William Henry Harrison defeats Tecumseh's confederacy at Tippecanoe.
Dec 16 The first of the New Madrid earthquakes shakes the central US.
Mar 13 The Comet of 1811 becomes visible to the naked eye, remaining so for 260 days.
Jul 5 Venezuela declares independence from Spain.

Events compiled from Wikipedia ↗ · Licensed CC BY-SA 4.0

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, 1811
Ended on: Tuesday
December 31, 1811
Friday the 13ths: 2
2 Friday the 13ths this year.
Easter Sunday: April 14
Sunday, April 14, 1811
Decade: 1810s
1810–1819
Century: 19th century
1801–1900
Millennium: 2nd millennium
1001–2000
Years ago: 215
215 years before 2026.

In other calendars

Hebrew: 5571 / 5572 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1225 / 1226 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Goat
Sexagenary cycle position 8 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 2354 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1189 / 1190 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1803 / 1804 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1733 / 1732 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 4
Digit sum: 11
Digit product: 8
Digital root: 2
Palindrome: No
Bit width: 11 bits
Reversed: 1,181
Flips to (rotate 180°): 1,181
Recamán's sequence: a(16,077) = 1,811
Square (n²): 3,279,721
Cube (n³): 5,939,574,731
Divisor count: 2
σ(n) — sum of divisors: 1,812
φ(n) — Euler's totient: 1,810

Primality

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

Divisors & multiples

All divisors (2)

1 · 1811

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 1,811)

1 × 1811

First multiples

1,811 · 3,622 (double) · 5,433 · 7,244 · 9,055 · 10,866 · 12,677 · 14,488 · 16,299 · 18,110

Sums & aliquot sequence

As consecutive integers: 905 + 906

Continued fraction of √n

√1,811 = [42; (1, 1, 3, 1, 41, 1, 3, 1, 1, 84)]

Period length 10 — the block in parentheses repeats forever.

Representations

In words: one thousand eight hundred eleven
Ordinal: 1811th
Roman numeral: MDCCCXI
Binary: 11100010011
Octal: 3423
Hexadecimal: 0x713
Base64: BxM=
One's complement: 63,724 (16-bit)
Scientific notation: 1.811 × 10³
As a duration: 1,811 s = 30 minutes, 11 seconds

In other bases

ternary (3) 2111002

quaternary (4) 130103

quinary (5) 24221

senary (6) 12215

septenary (7) 5165

nonary (9) 2432

undecimal (11) 13a7

duodecimal (12) 106b

tridecimal (13) a94

tetradecimal (14) 935

pentadecimal (15) 80b

As an angle

1,811° = 5 × 360° + 11°

11° ≈ 0.192 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋 𒌋𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓏺
Greek (Milesian): ͵αωιαʹ
Mayan (base 20): 𝋤·𝋪·𝋫
Chinese: 一千八百一十一
Chinese (financial): 壹仟捌佰壹拾壹

In other modern scripts

Eastern Arabic ١٨١١ Devanagari १८११ Bengali ১৮১১ Tamil ௧௮௧௧ Thai ๑๘๑๑ Tibetan ༡༨༡༡ Khmer ១៨១១ Lao ໑໘໑໑ Burmese ၁၈၁၁

Digit at this position in famous constants

π — Pi (π): Digit 1,811 = 6
e — Euler's number (e): Digit 1,811 = 6
φ — Golden ratio (φ): Digit 1,811 = 7
√2 — Pythagoras's (√2): Digit 1,811 = 9
ln 2 — Natural log of 2: Digit 1,811 = 9
γ — Euler-Mascheroni (γ): Digit 1,811 = 1

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 1,801 (gap of 10)
Next prime: 1,823 (gap of 12)

Unicode codepoint

Syriac Letter Gamal

U+0713

Other letter (Lo)

UTF-8 encoding: DC 93 (2 bytes).

Lookup U+0713 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000713

RGB(0, 7, 19)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.19.

Address: 0.0.7.19
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.19

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

Musical pitch

Heard as a frequency, 1,811 Hz is closest to:

Concert pitch (A4 = 440 Hz): A6 (1760 Hz, +49¢ — about midway to A♯6)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, -13¢)
Baroque pitch (A4 = 415 Hz): B6 (1863.3 Hz, -49¢ — about midway to A♯6)

Position in π

The digit sequence 1811 first appears in π at position 7,432 of the decimal expansion (the 7,432ordinal-suffix:nd 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 1811 on Pi Search ↗