Number

643

643 is a prime, odd, a calendar year.

Arithmetic Number Cousin Prime Deficient Number Descending Digits Evil Number Prime Recamán's Sequence Squarefree Twin Prime Year

Historical context — 643 AD

Calendar year

Year 643 (DCXLIII) was a common year starting on Wednesday of the Julian calendar.

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Historical context — 643 BC

Calendar year

The year 643 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: 52
Started on: Sunday
January 1, 643
Ended on: Sunday
December 31, 643
Friday the 13ths: 2
2 Friday the 13ths this year.
Decade: 640s
640–649
Century: 7th century
601–700
Millennium: 1st millennium
1–1000
Years ago: 1,383
1383 years before 2026.

In other calendars

Hebrew: 4403 / 4404 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 22 / 23 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Water zodiac:Rabbit
Sexagenary cycle position 40 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1186 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 21 / 22 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 635 / 636 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 565 / 564 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 13
Digit product: 72
Digital root: 4
Palindrome: No
Bit width: 10 bits
Reversed: 346
Recamán's sequence: a(189) = 643
Square (n²): 413,449
Cube (n³): 265,847,707
Divisor count: 2
σ(n) — sum of divisors: 644
φ(n) — Euler's totient: 642

Primality

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

Divisors & multiples

All divisors (2)

1 · 643

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 643)

1 × 643

First multiples

643 · 1,286 (double) · 1,929 · 2,572 · 3,215 · 3,858 · 4,501 · 5,144 · 5,787 · 6,430

Sums & aliquot sequence

As consecutive integers: 321 + 322

Representations

In words: six hundred forty-three
Ordinal: 643rd
Roman numeral: DCXLIII
Binary: 1010000011
Octal: 1203
Hexadecimal: 0x283
Base64: AoM=
One's complement: 64,892 (16-bit)

In other bases

ternary (3) 212211

quaternary (4) 22003

quinary (5) 10033

senary (6) 2551

septenary (7) 1606

nonary (9) 784

undecimal (11) 535

duodecimal (12) 457

tridecimal (13) 3a6

tetradecimal (14) 33d

pentadecimal (15) 2cd

Historical numeral systems

Babylonian (base 60): 𒌋 𒌋𒌋𒌋𒌋𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓏺𓏺𓏺
Greek (Milesian): χμγʹ
Mayan (base 20): 𝋡·𝋬·𝋣
Chinese: 六百四十三
Chinese (financial): 陸佰肆拾參

In other modern scripts

Eastern Arabic ٦٤٣ Devanagari ६४३ Bengali ৬৪৩ Tamil ௬௪௩ Thai ๖๔๓ Tibetan ༦༤༣ Khmer ៦៤៣ Lao ໖໔໓ Burmese ၆၄၃

Digit at this position in famous constants

π — Pi (π): Digit 643 = 3
e — Euler's number (e): Digit 643 = 6
φ — Golden ratio (φ): Digit 643 = 6
√2 — Pythagoras's (√2): Digit 643 = 4
ln 2 — Natural log of 2: Digit 643 = 8
γ — Euler-Mascheroni (γ): Digit 643 = 4

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 641 (gap of 2)
Next prime: 647 (gap of 4)

Pair status: twin with 641, cousin with 647.

Unicode codepoint

Latin Small Letter Esh

U+0283

Lowercase letter (Ll)

UTF-8 encoding: CA 83 (2 bytes).

Lookup U+0283 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000283

RGB(0, 2, 131)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.131.

Address: 0.0.2.131
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.131

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