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Number

381

381 is a composite number, odd, a calendar year.

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

Historical context — 381 AD

Calendar year

Year 381 (CCCLXXXI) was a common year starting on Friday of the Julian calendar.

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Historical context — 381 BC

Calendar year

Year 381 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback Read the full article on Wikipedia →

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, 381
Ended on: Thursday
December 31, 381
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 380s
380–389
Century: 4th century
301–400
Millennium: 1st millennium
1–1000
Years ago: 1,645
1645 years before 2026.

In other calendars

Hebrew: 4141 / 4142 AM
Rosh Hashanah falls in September/October.
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: 924 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 373 / 374 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 303 / 302 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 12
Digit product: 24
Digital root: 3
Palindrome: No
Bit width: 9 bits
Reversed: 183
Recamán's sequence: a(2,490) = 381
Square (n²): 145,161
Cube (n³): 55,306,341
Divisor count: 4
σ(n) — sum of divisors: 512
φ(n) — Euler's totient: 252
Sum of prime factors: 130

Primality

Prime factorization: 3 × 127

Nearest primes: 379 (−2) · 383 (+2)

Divisors & multiples

All divisors (4)

1 · 3 · 127 · 381

Aliquot sum (sum of proper divisors): 131

Factor pairs (a × b = 381)

1 × 381

3 × 127

First multiples

381 · 762 (double) · 1,143 · 1,524 · 1,905 · 2,286 · 2,667 · 3,048 · 3,429 · 3,810

Sums & aliquot sequence

As consecutive integers: 190 + 191 126 + 127 + 128 61 + 62 + 63 + 64 + 65 + 66

Aliquot sequence: 381 → 131 → 1 → 0 — terminates at zero

Representations

In words: three hundred eighty-one
Ordinal: 381st
Roman numeral: CCCLXXXI
Binary: 101111101
Octal: 575
Hexadecimal: 0x17D
Base64: AX0=
One's complement: 65,154 (16-bit)

In other bases

ternary (3) 112010

quaternary (4) 11331

quinary (5) 3011

senary (6) 1433

septenary (7) 1053

nonary (9) 463

undecimal (11) 317

duodecimal (12) 279

tridecimal (13) 234

tetradecimal (14) 1d3

pentadecimal (15) 1a6

Historical numeral systems

Babylonian (base 60): 𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): τπαʹ
Mayan (base 20): 𝋳·𝋡
Chinese: 三百八十一
Chinese (financial): 參佰捌拾壹

In other modern scripts

Eastern Arabic ٣٨١ Devanagari ३८१ Bengali ৩৮১ Tamil ௩௮௧ Thai ๓๘๑ Tibetan ༣༨༡ Khmer ៣៨១ Lao ໓໘໑ Burmese ၃၈၁

Digit at this position in famous constants

π — Pi (π): Digit 381 = 2
e — Euler's number (e): Digit 381 = 4
φ — Golden ratio (φ): Digit 381 = 1
√2 — Pythagoras's (√2): Digit 381 = 1
ln 2 — Natural log of 2: Digit 381 = 8
γ — Euler-Mascheroni (γ): Digit 381 = 9

Also seen as

Unicode codepoint

Ž

Latin Capital Letter Z With Caron

U+017D

Uppercase letter (Lu)

UTF-8 encoding: C5 BD (2 bytes).

Lookup U+017D on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#00017D

RGB(0, 1, 125)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.1.125.

Address: 0.0.1.125
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.1.125

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