Number

1,866

1,866 is a composite number, even, a calendar year.

1,866 (one thousand eight hundred sixty-six) is an even 4-digit number. It is a composite number with 8 divisors, and factors as 2 × 3 × 311. Its proper divisors sum to 1,878, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is MDCCCLXVI and in binary, 11101001010.

Abundant Number Arithmetic Number Cube-Free Evil Number Flippable Recamán's Sequence Semiperfect Number Sphenic Number Squarefree Year

Interestingness

★ ★ ★ ★ ☆

7 notable facts · grade B

1,854 1,855 1,856 1,857 1,858 1,859 1,860 1,861 1,862 1,863 1,864 1,865 1,866 1,867 1,868 1,869 1,870 1,871 1,872 1,873 1,874 1,875 1,876 1,877 1,878

less more

Notable events — 1866 AD

Jul 3 Prussia decisively defeats Austria at Königgrätz, paving the way for German unification.
Jul 27 The first lasting transatlantic telegraph cable is laid.
Apr 9 The Civil Rights Act of 1866 is enacted over Andrew Johnson's veto.
Jun 20 Italy joins Prussia against Austria in the Third Italian War of Independence.
Dec 21 The Fetterman Fight near Fort Phil Kearny kills 81 US soldiers.

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: Monday
January 1, 1866
Ended on: Monday
December 31, 1866
Friday the 13ths: 2
2 Friday the 13ths this year.
Easter Sunday: April 1
Sunday, April 1, 1866
Decade: 1860s
1860–1869
Century: 19th century
1801–1900
Millennium: 2nd millennium
1001–2000
Years ago: 160
160 years before 2026.

In other calendars

Hebrew: 5626 / 5627 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1282 / 1283 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Fire zodiac:Tiger
Sexagenary cycle position 3 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 2409 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1244 / 1245 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1858 / 1859 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1788 / 1787 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 4
Digit sum: 21
Digit product: 288
Digital root: 3
Palindrome: No
Bit width: 11 bits
Reversed: 6,681
Flips to (rotate 180°): 9,981
Recamán's sequence: a(8,012) = 1,866
Square (n²): 3,481,956
Cube (n³): 6,497,329,896
Divisor count: 8
σ(n) — sum of divisors: 3,744
φ(n) — Euler's totient: 620
Sum of prime factors: 316

Primality

Prime factorization: 2 × 3 × 311

Nearest primes: 1,861 (−5) · 1,867 (+1)

Divisors & multiples

All divisors (8)

1 · 2 · 3 · 6 · 311 · 622 · 933 (half) · 1866

Aliquot sum (sum of proper divisors): 1,878

Factor pairs (a × b = 1,866)

1 × 1866

2 × 933

3 × 622

6 × 311

First multiples

1,866 · 3,732 (double) · 5,598 · 7,464 · 9,330 · 11,196 · 13,062 · 14,928 · 16,794 · 18,660

Sums & aliquot sequence

As consecutive integers: 621 + 622 + 623 465 + 466 + 467 + 468 150 + 151 + … + 161

Aliquot sequence: 1,866 → 1,878 → 1,890 → 3,870 → 6,426 → 10,854 → 13,830 → 19,434 → 20,886 → 21,606 → 25,098 → 26,742 → 26,754 → 40,446 → 63,234 → 77,406 → 110,754 — unresolved within range

Continued fraction of √n

√1,866 = [43; (5, 14, 5, 86)]

Period length 4 — the block in parentheses repeats forever.

Representations

In words: one thousand eight hundred sixty-six
Ordinal: 1866th
Roman numeral: MDCCCLXVI
Binary: 11101001010
Octal: 3512
Hexadecimal: 0x74A
Base64: B0o=
One's complement: 63,669 (16-bit)
Scientific notation: 1.866 × 10³
As a duration: 1,866 s = 31 minutes, 6 seconds

In other bases

ternary (3) 2120010

quaternary (4) 131022

quinary (5) 24431

senary (6) 12350

septenary (7) 5304

nonary (9) 2503

undecimal (11) 1447

duodecimal (12) 10b6

tridecimal (13) b07

tetradecimal (14) 974

pentadecimal (15) 846

As an angle

1,866° = 5 × 360° + 66°

66° ≈ 1.152 rad

Compass bearing: ENE (east-northeast)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋𒁹 𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ͵αωξϛʹ
Mayan (base 20): 𝋤·𝋭·𝋦
Chinese: 一千八百六十六
Chinese (financial): 壹仟捌佰陸拾陸

In other modern scripts

Eastern Arabic ١٨٦٦ Devanagari १८६६ Bengali ১৮৬৬ Tamil ௧௮௬௬ Thai ๑๘๖๖ Tibetan ༡༨༦༦ Khmer ១៨៦៦ Lao ໑໘໖໖ Burmese ၁၈၆၆

Digit at this position in famous constants

π — Pi (π): Digit 1,866 = 2
e — Euler's number (e): Digit 1,866 = 6
φ — Golden ratio (φ): Digit 1,866 = 4
√2 — Pythagoras's (√2): Digit 1,866 = 6
ln 2 — Natural log of 2: Digit 1,866 = 0
γ — Euler-Mascheroni (γ): Digit 1,866 = 9

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 1866, here are decompositions:

5 + 1861 = 1866
19 + 1847 = 1866
43 + 1823 = 1866
79 + 1787 = 1866
83 + 1783 = 1866
89 + 1777 = 1866
107 + 1759 = 1866
113 + 1753 = 1866

Showing the first eight; more decompositions exist.

Unicode codepoint

Syriac Barrekh

U+074A

Non-spacing mark (Mn)

UTF-8 encoding: DD 8A (2 bytes).

Lookup U+074A on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#00074A

RGB(0, 7, 74)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.74.

Address: 0.0.7.74
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.74

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

Musical pitch

Heard as a frequency, 1,866 Hz is closest to:

Concert pitch (A4 = 440 Hz): A♯6 (1864.7 Hz, +1¢)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, +39¢)
Baroque pitch (A4 = 415 Hz): B6 (1863.3 Hz, +3¢)

Position in π

The digit sequence 1866 first appears in π at position 3,149 of the decimal expansion (the 3,149ordinal-suffix:th 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 1866 on Pi Search ↗