Number

1,800

1,800 is a composite number, even, a calendar year.

1,800 (one thousand eight hundred) is an even 4-digit number. It is a composite number with 36 divisors, and factors as 2³ × 3² × 5². Its proper divisors sum to 4,245, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is MDCCC and in binary, 11100001000.

Abundant Number Achilles Number Evil Number Flippable Gapful Number Harshad / Niven Highly Abundant Pentagonal Pyramidal Powerful Number Practical Number Preferred Number Recamán's Sequence Refactorable Number Semiperfect Number Year

Interestingness

★ ★ ★ ★ ★

12 notable facts · grade A

1,788 1,789 1,790 1,791 1,792 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

less more

Notable events — 1800 AD

Apr 24 Congress authorizes the Library of Congress.
Jun 14 Napoleon defeats the Austrians at Marengo.
Nov 17 The US Congress holds its first session in Washington, D.C.
Dec 3 Thomas Jefferson and Aaron Burr tie in the electoral college; the House decides for Jefferson in February.
May 7 The Indiana Territory is organized.

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, 1800
Ended on: Wednesday
December 31, 1800
Friday the 13ths: 1
One Friday the 13th this year.
Easter Sunday: April 13
Sunday, April 13, 1800
Decade: 1800s
1800–1809
Century: 18th century
1701–1800
Millennium: 2nd millennium
1001–2000
Years ago: 226
226 years before 2026.
US presidential election: Yes
US holds a presidential election in years divisible by 4 starting from 1788.

In other calendars

Hebrew: 5560 / 5561 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1214 / 1215 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Monkey
Sexagenary cycle position 57 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 2343 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1178 / 1179 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1792 / 1793 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1722 / 1721 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 4
Digit sum: 9
Digit product: 0
Digital root: 9
Palindrome: No
Bit width: 11 bits
Reversed: 81
Flips to (rotate 180°): 81
Recamán's sequence: a(16,099) = 1,800
Square (n²): 3,240,000
Cube (n³): 5,832,000,000
Divisor count: 36
σ(n) — sum of divisors: 6,045
φ(n) — Euler's totient: 480
Sum of prime factors: 22

Primality

Prime factorization: 2 ³ × 3 ² × 5 ²

Nearest primes: 1,789 (−11) · 1,801 (+1)

Divisors & multiples

All divisors (36)

1 · 2 · 3 · 4 · 5 · 6 · 8 · 9 · 10 · 12 · 15 · 18 · 20 · 24 · 25 · 30 · 36 · 40 · 45 · 50 · 60 · 72 · 75 · 90 · 100 · 120 · 150 · 180 · 200 · 225 · 300 · 360 · 450 · 600 · 900 (half) · 1800

Aliquot sum (sum of proper divisors): 4,245

Factor pairs (a × b = 1,800)

1 × 1800

2 × 900

3 × 600

4 × 450

5 × 360

6 × 300

8 × 225

9 × 200

10 × 180

12 × 150

15 × 120

18 × 100

20 × 90

24 × 75

25 × 72

30 × 60

36 × 50

40 × 45

First multiples

1,800 · 3,600 (double) · 5,400 · 7,200 · 9,000 · 10,800 · 12,600 · 14,400 · 16,200 · 18,000

Sums & aliquot sequence

As a sum of two squares: 6² + 42² = 30² + 30²

As consecutive integers: 599 + 600 + 601 358 + 359 + 360 + 361 + 362 196 + 197 + … + 204 113 + 114 + … + 127

Aliquot sequence: 1,800 → 4,245 → 2,571 → 861 → 483 → 285 → 195 → 141 → 51 → 21 → 11 → 1 → 0 — terminates at zero

Continued fraction of √n

√1,800 = [42; (2, 2, 1, 8, 1, 2, 2, 84)]

Period length 8 — the block in parentheses repeats forever.

Representations

In words: one thousand eight hundred
Ordinal: 1800th
Roman numeral: MDCCC
Binary: 11100001000
Octal: 3410
Hexadecimal: 0x708
Base64: Bwg=
One's complement: 63,735 (16-bit)
Scientific notation: 1.8 × 10³
As a duration: 1,800 s = 30 minutes

In other bases

ternary (3) 2110200

quaternary (4) 130020

quinary (5) 24200

senary (6) 12200

septenary (7) 5151

nonary (9) 2420

undecimal (11) 1397

duodecimal (12) 1060

tridecimal (13) a86

tetradecimal (14) 928

pentadecimal (15) 800

As an angle

1,800° = 5 × 360°

0° ≈ 0 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋 ·
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢
Greek (Milesian): ͵αωʹ
Mayan (base 20): 𝋤·𝋪·𝋠
Chinese: 一千八百
Chinese (financial): 壹仟捌佰

In other modern scripts

Eastern Arabic ١٨٠٠ Devanagari १८०० Bengali ১৮০০ Tamil ௧௮௦௦ Thai ๑๘๐๐ Tibetan ༡༨༠༠ Khmer ១៨០០ Lao ໑໘໐໐ Burmese ၁၈၀၀

Digit at this position in famous constants

π — Pi (π): Digit 1,800 = 8
e — Euler's number (e): Digit 1,800 = 1
φ — Golden ratio (φ): Digit 1,800 = 8
√2 — Pythagoras's (√2): Digit 1,800 = 5
ln 2 — Natural log of 2: Digit 1,800 = 6
γ — Euler-Mascheroni (γ): Digit 1,800 = 1

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 1800, here are decompositions:

11 + 1789 = 1800
13 + 1787 = 1800
17 + 1783 = 1800
23 + 1777 = 1800
41 + 1759 = 1800
47 + 1753 = 1800
53 + 1747 = 1800
59 + 1741 = 1800

Showing the first eight; more decompositions exist.

Unicode codepoint

Syriac Supralinear Colon Skewed Left

U+0708

Other punctuation (Po)

UTF-8 encoding: DC 88 (2 bytes).

Lookup U+0708 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000708

RGB(0, 7, 8)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.8.

Address: 0.0.7.8
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.8

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

Musical pitch

Heard as a frequency, 1,800 Hz is closest to:

Concert pitch (A4 = 440 Hz): A6 (1760 Hz, +39¢)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, -23¢)
Baroque pitch (A4 = 415 Hz): A♯6 (1758.7 Hz, +40¢)

Position in π

The digit sequence 1800 first appears in π at position 23,738 of the decimal expansion (the 23,738ordinal-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 1800 on Pi Search ↗