Number

691

691 is a prime, odd, a calendar year.

Arithmetic Number Deficient Number Evil Number Flippable Prime Recamán's Sequence Squarefree Year

Historical context — 691 AD

Calendar year

Year 691 (DCXCI) was a common year starting on Sunday of the Julian calendar.

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Historical context — 691 BC

Decade

This article concerns the period 699 BC – 690 BC.

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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, 691
Ended on: Thursday
December 31, 691
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 690s
690–699
Century: 7th century
601–700
Millennium: 1st millennium
1–1000
Years ago: 1,335
1335 years before 2026.

In other calendars

Hebrew: 4451 / 4452 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 71 / 72 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Rabbit
Sexagenary cycle position 28 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1234 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 69 / 70 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 683 / 684 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 613 / 612 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 16
Digit product: 54
Digital root: 7
Palindrome: No
Bit width: 10 bits
Reversed: 196
Flips to (rotate 180°): 169
Recamán's sequence: a(2,242) = 691
Square (n²): 477,481
Cube (n³): 329,939,371
Divisor count: 2
σ(n) — sum of divisors: 692
φ(n) — Euler's totient: 690

Primality

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

Divisors & multiples

All divisors (2)

1 · 691

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 691)

1 × 691

First multiples

691 · 1,382 (double) · 2,073 · 2,764 · 3,455 · 4,146 · 4,837 · 5,528 · 6,219 · 6,910

Sums & aliquot sequence

As consecutive integers: 345 + 346

Representations

In words: six hundred ninety-one
Ordinal: 691st
Roman numeral: DCXCI
Binary: 1010110011
Octal: 1263
Hexadecimal: 0x2B3
Base64: ArM=
One's complement: 64,844 (16-bit)

In other bases

ternary (3) 221121

quaternary (4) 22303

quinary (5) 10231

senary (6) 3111

septenary (7) 2005

nonary (9) 847

undecimal (11) 579

duodecimal (12) 497

tridecimal (13) 412

tetradecimal (14) 375

pentadecimal (15) 311

Historical numeral systems

Babylonian (base 60): 𒌋𒁹 𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): χϟαʹ
Mayan (base 20): 𝋡·𝋮·𝋫
Chinese: 六百九十一
Chinese (financial): 陸佰玖拾壹

In other modern scripts

Eastern Arabic ٦٩١ Devanagari ६९१ Bengali ৬৯১ Tamil ௬௯௧ Thai ๖๙๑ Tibetan ༦༩༡ Khmer ៦៩១ Lao ໖໙໑ Burmese ၆၉၁

Digit at this position in famous constants

π — Pi (π): Digit 691 = 9
e — Euler's number (e): Digit 691 = 2
φ — Golden ratio (φ): Digit 691 = 6
√2 — Pythagoras's (√2): Digit 691 = 0
ln 2 — Natural log of 2: Digit 691 = 6
γ — Euler-Mascheroni (γ): Digit 691 = 3

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 683 (gap of 8)
Next prime: 701 (gap of 10)

Unicode codepoint

Modifier Letter Small R

U+02B3

Modifier letter (Lm)

UTF-8 encoding: CA B3 (2 bytes).

Lookup U+02B3 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#0002B3

RGB(0, 2, 179)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.179.

Address: 0.0.2.179
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.179

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