Number

999

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

999 (nine hundred ninety-nine) is an odd 3-digit number. It is a composite number with 8 divisors, and factors as 3³ × 37. Its digits read the same forwards and backwards, so it is a palindromic number. Written other ways, in Roman numerals it is CMXCIX and in binary, 1111100111.

Arithmetic Number Deficient Number Evil Number Flippable Harshad / Niven Kaprekar Number Lucky Number Moran Number Palindrome Recamán's Sequence Repdigit Year

Interestingness

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9 notable facts · grade A

987 988 989 990 991 992 993 994 995 996 997 998 999 1,000 1,001 1,002 1,003 1,004 1,005 1,006 1,007 1,008 1,009 1,010 1,011

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Historical context — 999 AD

Calendar year

Year 999 (CMXCIX) was a common year starting on Sunday of the Julian calendar.

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

Historical context — 999 BC

Decade

The 990s BC is a decade that lasted from 999 BC to 990 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: Tuesday
January 1, 999
Ended on: Tuesday
December 31, 999
Friday the 13ths: 2
2 Friday the 13ths this year.
Decade: 990s
990–999
Century: 10th century
901–1000
Millennium: 1st millennium
1–1000
Years ago: 1,027
1027 years before 2026.

In other calendars

Hebrew: 4759 / 4760 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 389 / 390 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Earth zodiac:Pig
Sexagenary cycle position 36 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1542 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 377 / 378 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 991 / 992 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 921 / 920 Saka
Indian national calendar; year starts in March.

Cultural significance

Chinese lucky

Triple-9 — "forever forever forever"; long-lasting love.

九 (jiǔ) sounds like 久 ("eternal").

British significant

UK emergency telephone number (police/fire/ambulance).

Sourced from Wikipedia (Numerology, Chinese numerology, Gematria, and per-culture articles).

Properties

Parity: Odd
Digit count: 3
Digit sum: 27
Digit product: 729
Digital root: 9
Palindrome: Yes
Bit width: 10 bits
Flips to (rotate 180°): 666
Recamán's sequence: a(4,421) = 999
Square (n²): 998,001
Cube (n³): 997,002,999
Divisor count: 8
σ(n) — sum of divisors: 1,520
φ(n) — Euler's totient: 648
Sum of prime factors: 46

Primality

Prime factorization: 3 ³ × 37

Nearest primes: 997 (−2) · 1,009 (+10)

Divisors & multiples

All divisors (8)

1 · 3 · 9 · 27 · 37 · 111 · 333 · 999

Aliquot sum (sum of proper divisors): 521

Factor pairs (a × b = 999)

1 × 999

3 × 333

9 × 111

27 × 37

First multiples

999 · 1,998 (double) · 2,997 · 3,996 · 4,995 · 5,994 · 6,993 · 7,992 · 8,991 · 9,990

Sums & aliquot sequence

As consecutive integers: 499 + 500 332 + 333 + 334 164 + 165 + 166 + 167 + 168 + 169 107 + 108 + … + 115

Aliquot sequence: 999 → 521 → 1 → 0 — terminates at zero

Continued fraction of √n

√999 = [31; (1, 1, 1, 1, 5, 6, 1, 5, 2, 5, 1, 6, 5, 1, 1, 1, 1, 62)]

Period length 18 — the block in parentheses repeats forever.

Representations

In words: nine hundred ninety-nine
Ordinal: 999th
Roman numeral: CMXCIX
Binary: 1111100111
Octal: 1747
Hexadecimal: 0x3E7
Base64: A+c=
One's complement: 64,536 (16-bit)
Scientific notation: 9.99 × 10²
As a duration: 999 s = 16 minutes, 39 seconds

In other bases

ternary (3) 1101000

quaternary (4) 33213

quinary (5) 12444

senary (6) 4343

septenary (7) 2625

nonary (9) 1330

undecimal (11) 829

duodecimal (12) 6b3

tridecimal (13) 5bb

tetradecimal (14) 515

pentadecimal (15) 469

Palindromic in base 14

As an angle

999° = 2 × 360° + 279°

279° ≈ 4.869 rad

Compass bearing: W (west)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ϡϟθʹ
Mayan (base 20): 𝋢·𝋩·𝋳
Chinese: 九百九十九
Chinese (financial): 玖佰玖拾玖

In other modern scripts

Eastern Arabic ٩٩٩ Devanagari ९९९ Bengali ৯৯৯ Tamil ௯௯௯ Thai ๙๙๙ Tibetan ༩༩༩ Khmer ៩៩៩ Lao ໙໙໙ Burmese ၉၉၉

Digit at this position in famous constants

π — Pi (π): Digit 999 = 9
e — Euler's number (e): Digit 999 = 3
φ — Golden ratio (φ): Digit 999 = 3
√2 — Pythagoras's (√2): Digit 999 = 4
ln 2 — Natural log of 2: Digit 999 = 3
γ — Euler-Mascheroni (γ): Digit 999 = 3

Also seen as

Unicode codepoint

Coptic Small Letter Khei

U+03E7

Lowercase letter (Ll)

UTF-8 encoding: CF A7 (2 bytes).

Lookup U+03E7 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#0003E7

RGB(0, 3, 231)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.3.231.

Address: 0.0.3.231
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.3.231

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

Musical pitch

Heard as a frequency, 999 Hz is closest to:

Concert pitch (A4 = 440 Hz): B5 (987.8 Hz, +20¢)
Scientific pitch (C4 = 256 Hz): C6 (1024 Hz, -43¢)
Baroque pitch (A4 = 415 Hz): C6 (987 Hz, +21¢)