1,821
1,821 is a composite number, odd, a calendar year.
Notable events — 1821 AD
- May 5 Napoleon Bonaparte dies in exile on Saint Helena.
- Mar 25 The Greek War of Independence begins.
- Jul 28 Peru declares independence from Spain.
- Aug 24 The Treaty of Córdoba recognizes Mexican independence.
- Aug 10 Missouri becomes the 24th US state.
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, 1821
- Ended on
-
Monday
December 31, 1821
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Easter Sunday
-
April 22
Sunday, April 22, 1821
- Decade
-
1820s
1820–1829
- Century
-
19th century
1801–1900
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
205
205 years before 2026.
In other calendars
- Hebrew
-
5581 / 5582 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
1236 / 1237 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Metal zodiac:Snake
Sexagenary cycle position 18 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
2364 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
1199 / 1200 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1813 / 1814 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1743 / 1742 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 3 × 607
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- one thousand eight hundred twenty-one
- Ordinal
- 1821st
- Roman numeral
- MDCCCXXI
- Binary
- 11100011101
- Octal
- 3435
- Hexadecimal
- 0x71D
- Base64
- Bx0=
- One's complement
- 63,714 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒌋 𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓏺
- Greek (Milesian)
- ͵αωκαʹ
- Mayan (base 20)
- 𝋤·𝋫·𝋡
- Chinese
- 一千八百二十一
- Chinese (financial)
- 壹仟捌佰貳拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,821 = 5
- e — Euler's number (e)
- Digit 1,821 = 0
- φ — Golden ratio (φ)
- Digit 1,821 = 4
- √2 — Pythagoras's (√2)
- Digit 1,821 = 2
- ln 2 — Natural log of 2
- Digit 1,821 = 4
- γ — Euler-Mascheroni (γ)
- Digit 1,821 = 4
Also seen as
UTF-8 encoding: DC 9D (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.29.
- Address
- 0.0.7.29
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.7.29
Unspecified address (0.0.0.0/8) — "this network" placeholder.
This passes the ABA routing number checksum and matches the Federal Reserve numbering scheme.
Banks operate many routing numbers per state and division; an unmatched checksum-valid number can still be a real RTN at a smaller institution.
The digit sequence 1821 first appears in π at position 8,431 of the decimal expansion (the 8,431ordinal-suffix:st 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.