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Number

685

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

Arithmetic Number Deficient Number Evil Number Recamán's Sequence Semiprime Squarefree Year

Historical context — 685 AD

Calendar year

Year 685 (DCLXXXV) was a common year starting on Sunday of the Julian calendar.

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Historical context — 685 BC

Decade

This article concerns the period 689 BC – 680 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, 685
Ended on: Thursday
December 31, 685
Friday the 13ths: 3
3 Friday the 13ths this year.
Decade: 680s
680–689
Century: 7th century
601–700
Millennium: 1st millennium
1–1000
Years ago: 1,341
1341 years before 2026.

In other calendars

Hebrew: 4445 / 4446 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 65 / 66 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Wood zodiac:Rooster
Sexagenary cycle position 22 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1228 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 63 / 64 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 677 / 678 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 607 / 606 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 19
Digit product: 240
Digital root: 1
Palindrome: No
Bit width: 10 bits
Reversed: 586
Recamán's sequence: a(2,254) = 685
Square (n²): 469,225
Cube (n³): 321,419,125
Divisor count: 4
σ(n) — sum of divisors: 828
φ(n) — Euler's totient: 544
Sum of prime factors: 142

Primality

Prime factorization: 5 × 137

Nearest primes: 683 (−2) · 691 (+6)

Divisors & multiples

All divisors (4)

1 · 5 · 137 · 685

Aliquot sum (sum of proper divisors): 143

Factor pairs (a × b = 685)

1 × 685

5 × 137

First multiples

685 · 1,370 (double) · 2,055 · 2,740 · 3,425 · 4,110 · 4,795 · 5,480 · 6,165 · 6,850

Sums & aliquot sequence

As a sum of two squares: 3² + 26² = 18² + 19²

As consecutive integers: 342 + 343 135 + 136 + 137 + 138 + 139 64 + 65 + … + 73

Aliquot sequence: 685 → 143 → 25 → 6 → 6 — reaches a perfect number

Representations

In words: six hundred eighty-five
Ordinal: 685th
Roman numeral: DCLXXXV
Binary: 1010101101
Octal: 1255
Hexadecimal: 0x2AD
Base64: Aq0=
One's complement: 64,850 (16-bit)

In other bases

ternary (3) 221101

quaternary (4) 22231

quinary (5) 10220

senary (6) 3101

septenary (7) 1666

nonary (9) 841

undecimal (11) 573

duodecimal (12) 491

tridecimal (13) 409

tetradecimal (14) 36d

pentadecimal (15) 30a

Historical numeral systems

Babylonian (base 60): 𒌋𒁹 𒌋𒌋𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): χπεʹ
Mayan (base 20): 𝋡·𝋮·𝋥
Chinese: 六百八十五
Chinese (financial): 陸佰捌拾伍

In other modern scripts

Eastern Arabic ٦٨٥ Devanagari ६८५ Bengali ৬৮৫ Tamil ௬௮௫ Thai ๖๘๕ Tibetan ༦༨༥ Khmer ៦៨៥ Lao ໖໘໕ Burmese ၆၈၅

Digit at this position in famous constants

π — Pi (π): Digit 685 = 0
e — Euler's number (e): Digit 685 = 7
φ — Golden ratio (φ): Digit 685 = 6
√2 — Pythagoras's (√2): Digit 685 = 5
ln 2 — Natural log of 2: Digit 685 = 0
γ — Euler-Mascheroni (γ): Digit 685 = 4

Also seen as

Unicode codepoint

ʭ

Latin Letter Bidental Percussive

U+02AD

Lowercase letter (Ll)

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

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

Hex color

#0002AD

RGB(0, 2, 173)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.173.

Address: 0.0.2.173
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.2.173

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