Number

1,805

1,805 is a composite number, odd, a calendar year.

1,805 (one thousand eight hundred five) is an odd 4-digit number. It is a composite number with 6 divisors, and factors as 5 × 19². Written other ways, in Roman numerals it is MDCCCV and in binary, 11100001101.

Arithmetic Number Cube-Free Deficient Number Evil Number Recamán's Sequence Self Number Year

Interestingness

★ ★ ☆ ☆ ☆

4 notable facts · grade D

1,793 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

less more

Notable events — 1805 AD

Oct 21 Nelson defeats the Franco-Spanish fleet at Trafalgar; he is killed in the battle.
Dec 2 Napoleon decisively defeats the Russians and Austrians at Austerlitz.
Apr 27 US Marines storm Derna in Tripoli, the first US land action overseas.
Nov 7 Lewis and Clark reach the Pacific Ocean.
Dec 26 The Treaty of Pressburg dissolves the Holy Roman Empire's grip on Italy.

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, 1805
Ended on: Tuesday
December 31, 1805
Friday the 13ths: 2
2 Friday the 13ths this year.
Easter Sunday: April 14
Sunday, April 14, 1805
Decade: 1800s
1800–1809
Century: 19th century
1801–1900
Millennium: 2nd millennium
1001–2000
Years ago: 221
221 years before 2026.

In other calendars

Hebrew: 5565 / 5566 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1219 / 1220 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Wood zodiac:Ox
Sexagenary cycle position 2 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 2348 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1183 / 1184 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1797 / 1798 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1727 / 1726 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 4
Digit sum: 14
Digit product: 0
Digital root: 5
Palindrome: No
Bit width: 11 bits
Reversed: 5,081
Recamán's sequence: a(16,089) = 1,805
Square (n²): 3,258,025
Cube (n³): 5,880,735,125
Divisor count: 6
σ(n) — sum of divisors: 2,286
φ(n) — Euler's totient: 1,368
Sum of prime factors: 43

Primality

Prime factorization: 5 × 19 ²

Nearest primes: 1,801 (−4) · 1,811 (+6)

Divisors & multiples

All divisors (6)

1 · 5 · 19 · 95 · 361 · 1805

Aliquot sum (sum of proper divisors): 481

Factor pairs (a × b = 1,805)

1 × 1805

5 × 361

19 × 95

First multiples

1,805 · 3,610 (double) · 5,415 · 7,220 · 9,025 · 10,830 · 12,635 · 14,440 · 16,245 · 18,050

Sums & aliquot sequence

As a sum of two squares: 19² + 38²

As consecutive integers: 902 + 903 359 + 360 + 361 + 362 + 363 176 + 177 + … + 185 86 + 87 + … + 104

Aliquot sequence: 1,805 → 481 → 51 → 21 → 11 → 1 → 0 — terminates at zero

Continued fraction of √n

√1,805 = [42; (2, 16, 2, 84)]

Period length 4 — the block in parentheses repeats forever.

Representations

In words: one thousand eight hundred five
Ordinal: 1805th
Roman numeral: MDCCCV
Binary: 11100001101
Octal: 3415
Hexadecimal: 0x70D
Base64: Bw0=
One's complement: 63,730 (16-bit)
Scientific notation: 1.805 × 10³
As a duration: 1,805 s = 30 minutes, 5 seconds

In other bases

ternary (3) 2110212

quaternary (4) 130031

quinary (5) 24210

senary (6) 12205

septenary (7) 5156

nonary (9) 2425

undecimal (11) 13a1

duodecimal (12) 1065

tridecimal (13) a8b

tetradecimal (14) 92d

pentadecimal (15) 805

Palindromic in base 4

As an angle

1,805° = 5 × 360° + 5°

5° ≈ 0.087 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋 𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ͵αωεʹ
Mayan (base 20): 𝋤·𝋪·𝋥
Chinese: 一千八百零五
Chinese (financial): 壹仟捌佰零伍

In other modern scripts

Eastern Arabic ١٨٠٥ Devanagari १८०५ Bengali ১৮০৫ Tamil ௧௮௦௫ Thai ๑๘๐๕ Tibetan ༡༨༠༥ Khmer ១៨០៥ Lao ໑໘໐໕ Burmese ၁၈၀၅

Digit at this position in famous constants

π — Pi (π): Digit 1,805 = 9
e — Euler's number (e): Digit 1,805 = 5
φ — Golden ratio (φ): Digit 1,805 = 5
√2 — Pythagoras's (√2): Digit 1,805 = 5
ln 2 — Natural log of 2: Digit 1,805 = 0
γ — Euler-Mascheroni (γ): Digit 1,805 = 1

Also seen as

Unicode codepoint

Syriac Harklean Asteriscus

U+070D

Other punctuation (Po)

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

Lookup U+070D on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#00070D

RGB(0, 7, 13)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.13.

Address: 0.0.7.13
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.13

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

Musical pitch

Heard as a frequency, 1,805 Hz is closest to:

Concert pitch (A4 = 440 Hz): A6 (1760 Hz, +44¢)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, -19¢)
Baroque pitch (A4 = 415 Hz): A♯6 (1758.7 Hz, +45¢ — about midway to B6)

Position in π

The digit sequence 1805 first appears in π at position 10,959 of the decimal expansion (the 10,959ordinal-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 1805 on Pi Search ↗