Number

1,806

1,806 is a composite number, even, a calendar year.

1,806 (one thousand eight hundred six) is an even 4-digit number. It is a composite number with 16 divisors, and factors as 2 × 3 × 7 × 43. Its proper divisors sum to 2,418, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is MDCCCVI and in binary, 11100001110.

Abundant Number Arithmetic Number Cube-Free Evil Number Flippable Practical Number Pronic / Oblong Recamán's Sequence Semiperfect Number Squarefree Year

Interestingness

★ ★ ★ ★ ★

8 notable facts · grade A

1,794 1,795 1,796 1,797 1,798 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

less more

Notable events — 1806 AD

Jul 12 Napoleon establishes the Confederation of the Rhine.
Aug 6 Francis II abdicates as Holy Roman Emperor, ending the millennium-old empire.
Oct 14 Napoleon crushes Prussia at Jena-Auerstedt.
Nov 21 Napoleon issues the Berlin Decree initiating the Continental System.
Sep 23 The Lewis and Clark expedition returns to St. Louis.

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: Wednesday
January 1, 1806
Ended on: Wednesday
December 31, 1806
Friday the 13ths: 1
One Friday the 13th this year.
Easter Sunday: April 6
Sunday, April 6, 1806
Decade: 1800s
1800–1809
Century: 19th century
1801–1900
Millennium: 2nd millennium
1001–2000
Years ago: 220
220 years before 2026.

In other calendars

Hebrew: 5566 / 5567 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1220 / 1221 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: 2349 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1184 / 1185 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1798 / 1799 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1728 / 1727 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 4
Digit sum: 15
Digit product: 0
Digital root: 6
Palindrome: No
Bit width: 11 bits
Reversed: 6,081
Flips to (rotate 180°): 9,081
Recamán's sequence: a(16,087) = 1,806
Square (n²): 3,261,636
Cube (n³): 5,890,514,616
Divisor count: 16
σ(n) — sum of divisors: 4,224
φ(n) — Euler's totient: 504
Sum of prime factors: 55

Primality

Prime factorization: 2 × 3 × 7 × 43

Nearest primes: 1,801 (−5) · 1,811 (+5)

Divisors & multiples

All divisors (16)

1 · 2 · 3 · 6 · 7 · 14 · 21 · 42 · 43 · 86 · 129 · 258 · 301 · 602 · 903 (half) · 1806

Aliquot sum (sum of proper divisors): 2,418

Factor pairs (a × b = 1,806)

1 × 1806

2 × 903

3 × 602

6 × 301

7 × 258

14 × 129

21 × 86

42 × 43

First multiples

1,806 · 3,612 (double) · 5,418 · 7,224 · 9,030 · 10,836 · 12,642 · 14,448 · 16,254 · 18,060

Sums & aliquot sequence

As consecutive integers: 601 + 602 + 603 450 + 451 + 452 + 453 255 + 256 + … + 261 145 + 146 + … + 156

Aliquot sequence: 1,806 → 2,418 → 2,958 → 3,522 → 3,534 → 4,146 → 4,158 → 7,362 → 8,628 → 11,532 → 16,272 → 29,670 → 46,362 → 46,374 → 48,666 → 48,678 → 70,362 — unresolved within range

Continued fraction of √n

√1,806 = [42; (2, 84)]

Period length 2 — the block in parentheses repeats forever.

Representations

In words: one thousand eight hundred six
Ordinal: 1806th
Roman numeral: MDCCCVI
Binary: 11100001110
Octal: 3416
Hexadecimal: 0x70E
Base64: Bw4=
One's complement: 63,729 (16-bit)
Scientific notation: 1.806 × 10³
As a duration: 1,806 s = 30 minutes, 6 seconds

In other bases

ternary (3) 2110220

quaternary (4) 130032

quinary (5) 24211

senary (6) 12210

septenary (7) 5160

nonary (9) 2426

undecimal (11) 13a2

duodecimal (12) 1066

tridecimal (13) a8c

tetradecimal (14) 930

pentadecimal (15) 806

As an angle

1,806° = 5 × 360° + 6°

6° ≈ 0.105 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋 𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ͵αωϛʹ
Mayan (base 20): 𝋤·𝋪·𝋦
Chinese: 一千八百零六
Chinese (financial): 壹仟捌佰零陸

In other modern scripts

Eastern Arabic ١٨٠٦ Devanagari १८०६ Bengali ১৮০৬ Tamil ௧௮௦௬ Thai ๑๘๐๖ Tibetan ༡༨༠༦ Khmer ១៨០៦ Lao ໑໘໐໖ Burmese ၁၈၀၆

Digit at this position in famous constants

π — Pi (π): Digit 1,806 = 6
e — Euler's number (e): Digit 1,806 = 8
φ — Golden ratio (φ): Digit 1,806 = 5
√2 — Pythagoras's (√2): Digit 1,806 = 8
ln 2 — Natural log of 2: Digit 1,806 = 5
γ — Euler-Mascheroni (γ): Digit 1,806 = 6

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 1806, here are decompositions:

5 + 1801 = 1806
17 + 1789 = 1806
19 + 1787 = 1806
23 + 1783 = 1806
29 + 1777 = 1806
47 + 1759 = 1806
53 + 1753 = 1806
59 + 1747 = 1806

Showing the first eight; more decompositions exist.

Hex color

#00070E

RGB(0, 7, 14)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.14.

Address: 0.0.7.14
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.14

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

Musical pitch

Heard as a frequency, 1,806 Hz is closest to:

Concert pitch (A4 = 440 Hz): A6 (1760 Hz, +45¢ — about midway to A♯6)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, -18¢)
Baroque pitch (A4 = 415 Hz): A♯6 (1758.7 Hz, +46¢ — about midway to B6)

Position in π

The digit sequence 1806 first appears in π at position 5,488 of the decimal expansion (the 5,488ordinal-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 1806 on Pi Search ↗