Number

1,820

1,820 is a composite number, even, a calendar year.

1,820 (one thousand eight hundred twenty) is an even 4-digit number. It is a composite number with 24 divisors, and factors as 2² × 5 × 7 × 13. Its proper divisors sum to 2,884, more than the number itself, making it an abundant number. Written other ways, in Roman numerals it is MDCCCXX and in binary, 11100011100.

Abundant Number Arithmetic Number Cube-Free Evil Number Gapful Number Pentagonal Pentatope Number Practical Number Recamán's Sequence Semiperfect Number Year

Interestingness

★ ★ ★ ★ ★

8 notable facts · grade A

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 1,824 1,825 1,826 1,827 1,828 1,829 1,830 1,831 1,832

less more

Notable events — 1820 AD

Mar 6 Congress passes the Missouri Compromise admitting Missouri as a slave state.
Jan 29 George III dies after a 59-year reign; George IV succeeds him.
Jul 2 The Revolution of 1820 begins in Naples.
Mar 15 Maine becomes the 23rd US state.
Aug 11 The first arrivals of British settlers reach the Cape Colony in the "1820 settlers" scheme.

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

Year facts

Year type: Leap year
Divisible by 4 and not by 100; February has 29 days.
Days in year: 366
ISO weeks: 52
Started on: Saturday
January 1, 1820
Ended on: Sunday
December 31, 1820
Friday the 13ths: 1
One Friday the 13th this year.
Easter Sunday: April 2
Sunday, April 2, 1820
Decade: 1820s
1820–1829
Century: 19th century
1801–1900
Millennium: 2nd millennium
1001–2000
Years ago: 206
206 years before 2026.
US presidential election: Yes
US holds a presidential election in years divisible by 4 starting from 1788.

In other calendars

Hebrew: 5580 / 5581 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1235 / 1236 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Dragon
Sexagenary cycle position 17 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 2363 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1198 / 1199 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1812 / 1813 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1742 / 1741 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 4
Digit sum: 11
Digit product: 0
Digital root: 2
Palindrome: No
Bit width: 11 bits
Reversed: 281
Recamán's sequence: a(463) = 1,820
Square (n²): 3,312,400
Cube (n³): 6,028,568,000
Divisor count: 24
σ(n) — sum of divisors: 4,704
φ(n) — Euler's totient: 576
Sum of prime factors: 29

Primality

Prime factorization: 2 ² × 5 × 7 × 13

Nearest primes: 1,811 (−9) · 1,823 (+3)

Divisors & multiples

All divisors (24)

1 · 2 · 4 · 5 · 7 · 10 · 13 · 14 · 20 · 26 · 28 · 35 · 52 · 65 · 70 · 91 · 130 · 140 · 182 · 260 · 364 · 455 · 910 (half) · 1820

Aliquot sum (sum of proper divisors): 2,884

Factor pairs (a × b = 1,820)

1 × 1820

2 × 910

4 × 455

5 × 364

7 × 260

10 × 182

13 × 140

14 × 130

20 × 91

26 × 70

28 × 65

35 × 52

First multiples

1,820 · 3,640 (double) · 5,460 · 7,280 · 9,100 · 10,920 · 12,740 · 14,560 · 16,380 · 18,200

Sums & aliquot sequence

As consecutive integers: 362 + 363 + 364 + 365 + 366 257 + 258 + … + 263 224 + 225 + … + 231 134 + 135 + … + 146

Aliquot sequence: 1,820 → 2,884 → 2,940 → 6,636 → 11,284 → 13,804 → 16,436 → 16,492 → 19,348 → 19,404 → 42,840 → 125,640 → 283,860 → 633,420 → 1,562,004 → 2,535,180 → 5,206,260 — unresolved within range

Continued fraction of √n

√1,820 = [42; (1, 1, 1, 20, 1, 1, 1, 84)]

Period length 8 — the block in parentheses repeats forever.

Representations

In words: one thousand eight hundred twenty
Ordinal: 1820th
Roman numeral: MDCCCXX
Binary: 11100011100
Octal: 3434
Hexadecimal: 0x71C
Base64: Bxw=
One's complement: 63,715 (16-bit)
Scientific notation: 1.82 × 10³
As a duration: 1,820 s = 30 minutes, 20 seconds

In other bases

ternary (3) 2111102

quaternary (4) 130130

quinary (5) 24240

senary (6) 12232

septenary (7) 5210

nonary (9) 2442

undecimal (11) 1405

duodecimal (12) 1078

tridecimal (13) aa0

tetradecimal (14) 940

pentadecimal (15) 815

Palindromic in base 9

As an angle

1,820° = 5 × 360° + 20°

20° ≈ 0.349 rad

Compass bearing: NNE (north-northeast)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋 𒌋𒌋
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆
Greek (Milesian): ͵αωκʹ
Mayan (base 20): 𝋤·𝋫·𝋠
Chinese: 一千八百二十
Chinese (financial): 壹仟捌佰貳拾

In other modern scripts

Eastern Arabic ١٨٢٠ Devanagari १८२० Bengali ১৮২০ Tamil ௧௮௨௦ Thai ๑๘๒๐ Tibetan ༡༨༢༠ Khmer ១៨២០ Lao ໑໘໒໐ Burmese ၁၈၂၀

Digit at this position in famous constants

π — Pi (π): Digit 1,820 = 9
e — Euler's number (e): Digit 1,820 = 7
φ — Golden ratio (φ): Digit 1,820 = 4
√2 — Pythagoras's (√2): Digit 1,820 = 2
ln 2 — Natural log of 2: Digit 1,820 = 9
γ — Euler-Mascheroni (γ): Digit 1,820 = 5

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 1820, here are decompositions:

19 + 1801 = 1820
31 + 1789 = 1820
37 + 1783 = 1820
43 + 1777 = 1820
61 + 1759 = 1820
67 + 1753 = 1820
73 + 1747 = 1820
79 + 1741 = 1820

Showing the first eight; more decompositions exist.

Unicode codepoint

Syriac Letter Teth Garshuni

U+071C

Other letter (Lo)

UTF-8 encoding: DC 9C (2 bytes).

Lookup U+071C on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#00071C

RGB(0, 7, 28)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.28.

Address: 0.0.7.28
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.28

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

Musical pitch

Heard as a frequency, 1,820 Hz is closest to:

Concert pitch (A4 = 440 Hz): A♯6 (1864.7 Hz, -42¢)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, -4¢)
Baroque pitch (A4 = 415 Hz): B6 (1863.3 Hz, -41¢)

Position in π

The digit sequence 1820 first appears in π at position 24,653 of the decimal expansion (the 24,653ordinal-suffix:rd 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 1820 on Pi Search ↗