Number

1,921

1,921 is a composite number, odd, a calendar year.

Arithmetic Number Deficient Number Odious Number Pernicious Number Recamán's Sequence Semiprime Smith Number Squarefree Year

Notable events — 1921 AD

Mar 18 The Treaty of Riga ends the Polish-Soviet War.
May 19 The US Emergency Quota Act sharply curtails immigration.
May 31 The Tulsa race massacre destroys the Greenwood district.
Jul 11 A truce halts the Anglo-Irish War.
Jul 29 Adolf Hitler becomes leader of the Nazi Party.

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: Saturday
January 1, 1921
Ended on: Saturday
December 31, 1921
Friday the 13ths: 1
One Friday the 13th this year.
Easter Sunday: March 27
Sunday, March 27, 1921
Decade: 1920s
1920–1929
Century: 20th century
1901–2000
Millennium: 2nd millennium
1001–2000
Years ago: 105
105 years before 2026.

In other calendars

Hebrew: 5681 / 5682 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 1339 / 1340 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: 2464 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 1299 / 1300 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1913 / 1914 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1843 / 1842 Saka
Indian national calendar; year starts in March.
Japanese: Taishō 10
Reign-era counting from the start of each emperor's reign.

Properties

Parity: Odd
Digit count: 4
Digit sum: 13
Digit product: 18
Digital root: 4
Palindrome: No
Bit width: 11 bits
Reversed: 1,291
Recamán's sequence: a(7,902) = 1,921
Square (n²): 3,690,241
Cube (n³): 7,088,952,961
Divisor count: 4
σ(n) — sum of divisors: 2,052
φ(n) — Euler's totient: 1,792
Sum of prime factors: 130

Primality

Prime factorization: 17 × 113

Nearest primes: 1,913 (−8) · 1,931 (+10)

Divisors & multiples

All divisors (4)

1 · 17 · 113 · 1921

Aliquot sum (sum of proper divisors): 131

Factor pairs (a × b = 1,921)

1 × 1921

17 × 113

First multiples

1,921 · 3,842 (double) · 5,763 · 7,684 · 9,605 · 11,526 · 13,447 · 15,368 · 17,289 · 19,210

Sums & aliquot sequence

As a sum of two squares: 20² + 39² = 25² + 36²

As consecutive integers: 960 + 961 105 + 106 + … + 121 40 + 41 + … + 73

Aliquot sequence: 1,921 → 131 → 1 → 0 — terminates at zero

Representations

In words: one thousand nine hundred twenty-one
Ordinal: 1921st
Roman numeral: MCMXXI
Binary: 11110000001
Octal: 3601
Hexadecimal: 0x781
Base64: B4E=
One's complement: 63,614 (16-bit)

In other bases

ternary (3) 2122011

quaternary (4) 132001

quinary (5) 30141

senary (6) 12521

septenary (7) 5413

nonary (9) 2564

undecimal (11) 1497

duodecimal (12) 1141

tridecimal (13) b4a

tetradecimal (14) 9b3

pentadecimal (15) 881

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒌋𒁹𒁹 𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓏺
Greek (Milesian): ͵αϡκαʹ
Mayan (base 20): 𝋤·𝋰·𝋡
Chinese: 一千九百二十一
Chinese (financial): 壹仟玖佰貳拾壹

In other modern scripts

Eastern Arabic ١٩٢١ Devanagari १९२१ Bengali ১৯২১ Tamil ௧௯௨௧ Thai ๑๙๒๑ Tibetan ༡༩༢༡ Khmer ១៩២១ Lao ໑໙໒໑ Burmese ၁၉၂၁

Digit at this position in famous constants

π — Pi (π): Digit 1,921 = 5
e — Euler's number (e): Digit 1,921 = 2
φ — Golden ratio (φ): Digit 1,921 = 0
√2 — Pythagoras's (√2): Digit 1,921 = 6
ln 2 — Natural log of 2: Digit 1,921 = 5
γ — Euler-Mascheroni (γ): Digit 1,921 = 1

Also seen as

Unicode codepoint

Thaana Letter Shaviyani

U+0781

Other letter (Lo)

UTF-8 encoding: DE 81 (2 bytes).

Lookup U+0781 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000781

RGB(0, 7, 129)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.129.

Address: 0.0.7.129
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.7.129

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

Position in π

The digit sequence 1921 first appears in π at position 1,618 of the decimal expansion (the 1,618ordinal-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 1921 on Pi Search ↗