Number

641

641 is a prime, odd, a calendar year.

Arithmetic Number Chen Prime Deficient Number Descending Digits Odious Number Pernicious Number Prime Pythagorean Prime Recamán's Sequence Sexy Prime Sophie Germain Prime Squarefree Twin Prime Year

Historical context — 641 AD

Calendar year

Year 641 (DCXLI) was a common year starting on Monday of the Julian calendar.

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

Historical context — 641 BC

Calendar year

The year 641 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: Friday
January 1, 641
Ended on: Friday
December 31, 641
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 640s
640–649
Century: 7th century
601–700
Millennium: 1st millennium
1–1000
Years ago: 1,385
1385 years before 2026.

In other calendars

Hebrew: 4401 / 4402 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 20 / 21 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Ox
Sexagenary cycle position 38 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1184 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 19 / 20 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 633 / 634 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 563 / 562 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 11
Digit product: 24
Digital root: 2
Palindrome: No
Bit width: 10 bits
Reversed: 146
Recamán's sequence: a(4,637) = 641
Square (n²): 410,881
Cube (n³): 263,374,721
Divisor count: 2
σ(n) — sum of divisors: 642
φ(n) — Euler's totient: 640

Primality

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

Divisors & multiples

All divisors (2)

1 · 641

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 641)

1 × 641

First multiples

641 · 1,282 (double) · 1,923 · 2,564 · 3,205 · 3,846 · 4,487 · 5,128 · 5,769 · 6,410

Sums & aliquot sequence

As a sum of two squares: 4² + 25²

As consecutive integers: 320 + 321

Representations

In words: six hundred forty-one
Ordinal: 641st
Roman numeral: DCXLI
Binary: 1010000001
Octal: 1201
Hexadecimal: 0x281
Base64: AoE=
One's complement: 64,894 (16-bit)

In other bases

ternary (3) 212202

quaternary (4) 22001

quinary (5) 10031

senary (6) 2545

septenary (7) 1604

nonary (9) 782

undecimal (11) 533

duodecimal (12) 455

tridecimal (13) 3a4

tetradecimal (14) 33b

pentadecimal (15) 2cb

Historical numeral systems

Babylonian (base 60): 𒌋 𒌋𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): χμαʹ
Mayan (base 20): 𝋡·𝋬·𝋡
Chinese: 六百四十一
Chinese (financial): 陸佰肆拾壹

In other modern scripts

Eastern Arabic ٦٤١ Devanagari ६४१ Bengali ৬৪১ Tamil ௬௪௧ Thai ๖๔๑ Tibetan ༦༤༡ Khmer ៦៤១ Lao ໖໔໑ Burmese ၆၄၁

Digit at this position in famous constants

π — Pi (π): Digit 641 = 1
e — Euler's number (e): Digit 641 = 3
φ — Golden ratio (φ): Digit 641 = 3
√2 — Pythagoras's (√2): Digit 641 = 3
ln 2 — Natural log of 2: Digit 641 = 6
γ — Euler-Mascheroni (γ): Digit 641 = 7

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 631 (gap of 10)
Next prime: 643 (gap of 2)

Pair status: twin with 643.

Unicode codepoint

Latin Letter Small Capital Inverted R

U+0281

Lowercase letter (Ll)

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

Lookup U+0281 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000281

RGB(0, 2, 129)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.129.

Address: 0.0.2.129
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.129

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

NANP area code 641

The number 641 is an active NANP area code (North American Numbering Plan).

Primary area: North-central Iowa
Region: Iowa
Country: United States

Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.

Look up area code 641 ↗