Number

686

686 is a composite number, even, a calendar year.

686 (six hundred eighty-six) is an even 3-digit number. It is a composite number with 8 divisors, and factors as 2 × 7³. Its digits read the same forwards and backwards, so it is a palindromic number. Written other ways, in Roman numerals it is DCLXXXVI and in binary, 1010101110.

Arithmetic Number Deficient Number Evil Number Flippable Palindrome Recamán's Sequence Undulating Number Year

Interestingness

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5 notable facts · grade C

674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698

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Historical context — 686 AD

Calendar year

Year 686 (DCLXXXVI) was a common year starting on Monday of the Julian calendar.

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

Historical context — 686 BC

Decade

This article concerns the period 689 BC – 680 BC.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 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, 686
Ended on: Friday
December 31, 686
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 680s
680–689
Century: 7th century
601–700
Millennium: 1st millennium
1–1000
Years ago: 1,340
1340 years before 2026.

In other calendars

Hebrew: 4446 / 4447 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 66 / 67 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Fire zodiac:Dog
Sexagenary cycle position 23 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1229 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 64 / 65 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 678 / 679 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 608 / 607 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 3
Digit sum: 20
Digit product: 288
Digital root: 2
Palindrome: Yes
Bit width: 10 bits
Flips to (rotate 180°): 989
Recamán's sequence: a(2,252) = 686
Square (n²): 470,596
Cube (n³): 322,828,856
Divisor count: 8
σ(n) — sum of divisors: 1,200
φ(n) — Euler's totient: 294
Sum of prime factors: 23

Primality

Prime factorization: 2 × 7 ³

Nearest primes: 683 (−3) · 691 (+5)

Divisors & multiples

All divisors (8)

1 · 2 · 7 · 14 · 49 · 98 · 343 (half) · 686

Aliquot sum (sum of proper divisors): 514

Factor pairs (a × b = 686)

1 × 686

2 × 343

7 × 98

14 × 49

First multiples

686 · 1,372 (double) · 2,058 · 2,744 · 3,430 · 4,116 · 4,802 · 5,488 · 6,174 · 6,860

Sums & aliquot sequence

As a sum of two cubes: 7³ + 7³

As consecutive integers: 170 + 171 + 172 + 173 95 + 96 + … + 101 11 + 12 + … + 38

Aliquot sequence: 686 → 514 → 260 → 328 → 302 → 154 → 134 → 70 → 74 → 40 → 50 → 43 → 1 → 0 — terminates at zero

Continued fraction of √n

√686 = [26; (5, 4, 1, 1, 3, 2, 10, 26, 10, 2, 3, 1, 1, 4, 5, 52)]

Period length 16 — the block in parentheses repeats forever.

Representations

In words: six hundred eighty-six
Ordinal: 686th
Roman numeral: DCLXXXVI
Binary: 1010101110
Octal: 1256
Hexadecimal: 0x2AE
Base64: Aq4=
One's complement: 64,849 (16-bit)
Scientific notation: 6.86 × 10²
As a duration: 686 s = 11 minutes, 26 seconds

In other bases

ternary (3) 221102

quaternary (4) 22232

quinary (5) 10221

senary (6) 3102

septenary (7) 2000

nonary (9) 842

undecimal (11) 574

duodecimal (12) 492

tridecimal (13) 40a

tetradecimal (14) 370

pentadecimal (15) 30b

As an angle

686° = 1 × 360° + 326°

326° ≈ 5.69 rad

Compass bearing: NW (northwest)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹 𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): χπϛʹ
Mayan (base 20): 𝋡·𝋮·𝋦
Chinese: 六百八十六
Chinese (financial): 陸佰捌拾陸

In other modern scripts

Eastern Arabic ٦٨٦ Devanagari ६८६ Bengali ৬৮৬ Tamil ௬௮௬ Thai ๖๘๖ Tibetan ༦༨༦ Khmer ៦៨៦ Lao ໖໘໖ Burmese ၆၈၆

Digit at this position in famous constants

π — Pi (π): Digit 686 = 7
e — Euler's number (e): Digit 686 = 3
φ — Golden ratio (φ): Digit 686 = 7
√2 — Pythagoras's (√2): Digit 686 = 8
ln 2 — Natural log of 2: Digit 686 = 3
γ — Euler-Mascheroni (γ): Digit 686 = 4

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 686, here are decompositions:

3 + 683 = 686
13 + 673 = 686
43 + 643 = 686
67 + 619 = 686
73 + 613 = 686
79 + 607 = 686
109 + 577 = 686
139 + 547 = 686

Showing the first eight; more decompositions exist.

Unicode codepoint

Latin Small Letter Turned H With Fishhook

U+02AE

Lowercase letter (Ll)

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

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

Hex color

#0002AE

RGB(0, 2, 174)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.174.

Address: 0.0.2.174
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.174

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

Musical pitch

Heard as a frequency, 686 Hz is closest to:

Concert pitch (A4 = 440 Hz): F5 (698.5 Hz, -31¢)
Scientific pitch (C4 = 256 Hz): F5 (683.4 Hz, +6¢)
Baroque pitch (A4 = 415 Hz): F♯5 (697.9 Hz, -30¢)