Number

1,801

1,801 is a prime, odd, a calendar year.

1,801 (one thousand eight hundred one) is an odd 4-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in Roman numerals it is MDCCCI and in binary, 11100001001.

Arithmetic Number Centered Hexagonal Chen Prime Cuban Prime Cube-Free Deficient Number Flippable Odious Number Pernicious Number Prime Pythagorean Prime Recamán's Sequence Squarefree Year

Interestingness

★ ★ ★ ★ ★

10 notable facts · grade A

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 1,813

less more

Notable events — 1801 AD

Jan 1 The Acts of Union form the United Kingdom of Great Britain and Ireland.
Mar 4 Thomas Jefferson is inaugurated as the third US president.
Apr 2 Nelson defeats the Danes at the Battle of Copenhagen.
Jul 15 Napoleon signs a Concordat with Pope Pius VII restoring the Catholic Church in France.
Jan 1 Giuseppe Piazzi discovers Ceres, the first known asteroid.

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: 53
Long year: contains 53 ISO weeks.
Started on: Thursday
January 1, 1801
Ended on: Thursday
December 31, 1801
Friday the 13ths: 3
3 Friday the 13ths this year.
Easter Sunday: April 5
Sunday, April 5, 1801
Decade: 1800s
1800–1809
Century: 19th century
1801–1900
Millennium: 2nd millennium
1001–2000
Years ago: 225
225 years before 2026.

In other calendars

Hebrew: 5561 / 5562 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1215 / 1216 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Rooster
Sexagenary cycle position 58 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 2344 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1179 / 1180 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1793 / 1794 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1723 / 1722 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 4
Digit sum: 10
Digit product: 0
Digital root: 1
Palindrome: No
Bit width: 11 bits
Reversed: 1,081
Flips to (rotate 180°): 1,081
Recamán's sequence: a(16,097) = 1,801
Square (n²): 3,243,601
Cube (n³): 5,841,725,401
Divisor count: 2
σ(n) — sum of divisors: 1,802
φ(n) — Euler's totient: 1,800

Primality

1,801 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 1801

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 1,801)

1 × 1801

First multiples

1,801 · 3,602 (double) · 5,403 · 7,204 · 9,005 · 10,806 · 12,607 · 14,408 · 16,209 · 18,010

Sums & aliquot sequence

As a sum of two squares: 24² + 35²

As consecutive integers: 900 + 901

Continued fraction of √n

√1,801 = [42; (2, 3, 1, 1, 5, 10, 2, 3, 16, 1, 2, 4, 1, 27, 2, 11, 1, 1, 1, 2, 1, 2, 1, 4, …)]

Representations

In words: one thousand eight hundred one
Ordinal: 1801st
Roman numeral: MDCCCI
Binary: 11100001001
Octal: 3411
Hexadecimal: 0x709
Base64: Bwk=
One's complement: 63,734 (16-bit)
Scientific notation: 1.801 × 10³
As a duration: 1,801 s = 30 minutes, 1 second

In other bases

ternary (3) 2110201

quaternary (4) 130021

quinary (5) 24201

senary (6) 12201

septenary (7) 5152

nonary (9) 2421

undecimal (11) 1398

duodecimal (12) 1061

tridecimal (13) a87

tetradecimal (14) 929

pentadecimal (15) 801

Palindromic in base 14

As an angle

1,801° = 5 × 360° + 1°

1° ≈ 0.017 rad

Compass bearing: N (north)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋 𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓏺
Greek (Milesian): ͵αωαʹ
Mayan (base 20): 𝋤·𝋪·𝋡
Chinese: 一千八百零一
Chinese (financial): 壹仟捌佰零壹

In other modern scripts

Eastern Arabic ١٨٠١ Devanagari १८०१ Bengali ১৮০১ Tamil ௧௮௦௧ Thai ๑๘๐๑ Tibetan ༡༨༠༡ Khmer ១៨០១ Lao ໑໘໐໑ Burmese ၁၈၀၁

Digit at this position in famous constants

π — Pi (π): Digit 1,801 = 3
e — Euler's number (e): Digit 1,801 = 0
φ — Golden ratio (φ): Digit 1,801 = 9
√2 — Pythagoras's (√2): Digit 1,801 = 4
ln 2 — Natural log of 2: Digit 1,801 = 7
γ — Euler-Mascheroni (γ): Digit 1,801 = 0

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 1,789 (gap of 12)
Next prime: 1,811 (gap of 10)

Unicode codepoint

Syriac Sublinear Colon Skewed Right

U+0709

Other punctuation (Po)

UTF-8 encoding: DC 89 (2 bytes).

Lookup U+0709 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000709

RGB(0, 7, 9)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.9.

Address: 0.0.7.9
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.9

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

Musical pitch

Heard as a frequency, 1,801 Hz is closest to:

Concert pitch (A4 = 440 Hz): A6 (1760 Hz, +40¢)
Scientific pitch (C4 = 256 Hz): A♯6 (1824.6 Hz, -23¢)
Baroque pitch (A4 = 415 Hz): A♯6 (1758.7 Hz, +41¢)

Position in π

The digit sequence 1801 first appears in π at position 12,256 of the decimal expansion (the 12,256ordinal-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 1801 on Pi Search ↗