Number

990

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

990 (nine hundred ninety) is an even 3-digit number. It is a composite number with 24 divisors, and factors as 2 × 3² × 5 × 11. Its proper divisors sum to 1,818, more than the number itself, making it an abundant number. It is the 44th triangular number. Written other ways, in Roman numerals it is CMXC and in binary, 1111011110.

Abundant Number Arithmetic Number Cube-Free Evil Number Flippable Gapful Number Harshad / Niven Practical Number Recamán's Sequence Semiperfect Number Triangular Year

Interestingness

★ ★ ★ ★ ★

9 notable facts · grade A

978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1,000 1,001 1,002

less more

Historical context — 990 AD

Calendar year

Year 990 (CMXC) was a common year starting on Wednesday of the Julian calendar.

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

Historical context — 990 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: Friday
January 1, 990
Ended on: Friday
December 31, 990
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 990s
990–999
Century: 10th century
901–1000
Millennium: 1st millennium
1–1000
Years ago: 1,036
1036 years before 2026.

In other calendars

Hebrew: 4750 / 4751 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 379 / 380 AH
Lunar calendar; year spans differ from Gregorian.
Chinese: Year of the zodiac:Metal zodiac:Tiger
Sexagenary cycle position 27 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 1533 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 368 / 369 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 982 / 983 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 912 / 911 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 3
Digit sum: 18
Digit product: 0
Digital root: 9
Palindrome: No
Bit width: 10 bits
Reversed: 99
Flips to (rotate 180°): 66
Recamán's sequence: a(4,439) = 990
Square (n²): 980,100
Cube (n³): 970,299,000
Divisor count: 24
σ(n) — sum of divisors: 2,808
φ(n) — Euler's totient: 240
Sum of prime factors: 24

Primality

Prime factorization: 2 × 3 ² × 5 × 11

Nearest primes: 983 (−7) · 991 (+1)

Divisors & multiples

All divisors (24)

1 · 2 · 3 · 5 · 6 · 9 · 10 · 11 · 15 · 18 · 22 · 30 · 33 · 45 · 55 · 66 · 90 · 99 · 110 · 165 · 198 · 330 · 495 (half) · 990

Aliquot sum (sum of proper divisors): 1,818

Factor pairs (a × b = 990)

1 × 990

2 × 495

3 × 330

5 × 198

6 × 165

9 × 110

10 × 99

11 × 90

15 × 66

18 × 55

22 × 45

30 × 33

First multiples

990 · 1,980 (double) · 2,970 · 3,960 · 4,950 · 5,940 · 6,930 · 7,920 · 8,910 · 9,900

Sums & aliquot sequence

As consecutive integers: 329 + 330 + 331 246 + 247 + 248 + 249 196 + 197 + 198 + 199 + 200 106 + 107 + … + 114

Aliquot sequence: 990 → 1,818 → 2,160 → 5,280 → 12,864 → 21,680 → 28,912 → 31,848 → 47,832 → 71,808 → 148,512 → 359,520 → 946,848 → 1,895,712 → 4,539,360 → 12,180,336 → 23,781,648 — unresolved within range

Continued fraction of √n

√990 = [31; (2, 6, 2, 62)]

Period length 4 — the block in parentheses repeats forever.

Representations

In words: nine hundred ninety
Ordinal: 990th
Roman numeral: CMXC
Binary: 1111011110
Octal: 1736
Hexadecimal: 0x3DE
Base64: A94=
One's complement: 64,545 (16-bit)
Scientific notation: 9.9 × 10²
As a duration: 990 s = 16 minutes, 30 seconds

In other bases

ternary (3) 1100200

quaternary (4) 33132

quinary (5) 12430

senary (6) 4330

septenary (7) 2613

nonary (9) 1320

undecimal (11) 820

duodecimal (12) 6a6

tridecimal (13) 5b2

tetradecimal (14) 50a

pentadecimal (15) 460

Palindromic in base 12

As an angle

990° = 2 × 360° + 270°

270° ≈ 4.712 rad

Compass bearing: W (west)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋
Egyptian hieroglyphic: 𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆
Greek (Milesian): ϡϟʹ
Mayan (base 20): 𝋢·𝋩·𝋪
Chinese: 九百九十
Chinese (financial): 玖佰玖拾

In other modern scripts

Eastern Arabic ٩٩٠ Devanagari ९९० Bengali ৯৯০ Tamil ௯௯௦ Thai ๙๙๐ Tibetan ༩༩༠ Khmer ៩៩០ Lao ໙໙໐ Burmese ၉၉၀

Digit at this position in famous constants

π — Pi (π): Digit 990 = 0
e — Euler's number (e): Digit 990 = 8
φ — Golden ratio (φ): Digit 990 = 2
√2 — Pythagoras's (√2): Digit 990 = 2
ln 2 — Natural log of 2: Digit 990 = 7
γ — Euler-Mascheroni (γ): Digit 990 = 2

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 990, here are decompositions:

7 + 983 = 990
13 + 977 = 990
19 + 971 = 990
23 + 967 = 990
37 + 953 = 990
43 + 947 = 990
53 + 937 = 990
61 + 929 = 990

Showing the first eight; more decompositions exist.

Unicode codepoint

Greek Letter Koppa

U+03DE

Uppercase letter (Lu)

UTF-8 encoding: CF 9E (2 bytes).

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

Network port

TCP/UDP port 990 is the well-known port for FTPS — FTP over TLS — control channel.

Hex color

#0003DE

RGB(0, 3, 222)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.3.222.

Address: 0.0.3.222
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.3.222

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

Musical pitch

Heard as a frequency, 990 Hz is closest to:

Concert pitch (A4 = 440 Hz): B5 (987.8 Hz, +4¢)
Scientific pitch (C4 = 256 Hz): B5 (966.5 Hz, +42¢)
Baroque pitch (A4 = 415 Hz): C6 (987 Hz, +5¢)