Number

8

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

8 (eight) is an even 1-digit number. It is a composite number with 4 divisors, and factors as 2³. It is a perfect cube (2³), a Fibonacci number, and a power of two (2³). Written other ways, in Roman numerals it is VIII and in binary, 1000.

Cake Number Deficient Number Fibonacci Flippable Harshad / Niven Highly Abundant Leyland Number Lucky Number Narcissistic / Armstrong Octagonal Odious Number Perfect Cube Power of Two Powerful Number Practical Number Recamán's Sequence Refactorable Number Strobogrammatic Tetranacci Number Year Zuckerman Number

Interestingness

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18 notable facts · grade A

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Historical context — 8 AD

First 9 years of the Common Era

The 0s began on January 1, AD 1 and ended on December 31, AD 9, covering the first nine years of the Common Era.

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

Historical context — 8 BC

Calendar year

Year 8 BC was either a common year starting on Friday or Saturday or a leap year starting on Thursday of the Julian calendar and a common year starting on Wednesday of the Proleptic Julian calendar.

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

Year facts

Year type: Leap year
Divisible by 4 and not by 100; February has 29 days.
Days in year: 366
ISO weeks: 52
Started on: Tuesday
January 1, 8
Ended on: Wednesday
December 31, 8
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 0s
0–9
Century: 1st century
1–100
Millennium: 1st millennium
1–1000
Years ago: 2,018
2018 years before 2026.

In other calendars

Hebrew: 3768 / 3769 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Earth zodiac:Dragon
Sexagenary cycle position 5 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 551 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 0 / 1 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): -70 / -71 Saka
Indian national calendar; year starts in March.

Cultural significance

Chinese lucky

Extremely lucky — sought after in addresses, phone numbers, license plates.

八 (bā) sounds like 发 (fā, "prosper, get rich"). The Beijing Olympics opened on 08/08/08 at 8:08 PM.

Wikipedia ↗

Japanese lucky

Lucky — represents prosperity broadening like an opening fan.

The shape of the kanji 八 widens outward.

Hindu sacred

Associated with Lakshmi and the eight forms of wealth (Ashta Lakshmi).

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

Properties

Parity: Even
Digit count: 1
Digit sum: 8
Digital root: 8
Palindrome: Yes
Bit width: 4 bits
Recamán's sequence: a(16) = 8
Square (n²): 64
Cube (n³): 512
Cube root (∛n): 2
Divisor count: 4
σ(n) — sum of divisors: 15
φ(n) — Euler's totient: 4
Sum of prime factors: 6

Primality

Prime factorization: 2 ³

Nearest primes: 7 (−1) · 11 (+3)

Divisors & multiples

All divisors (4)

1 · 2 · 4 (half) · 8

Aliquot sum (sum of proper divisors): 7

Factor pairs (a × b = 8)

1 × 8

2 × 4

First multiples

8 · 16 (double) · 24 · 32 · 40 · 48 · 56 · 64 · 72 · 80

Sums & aliquot sequence

As a sum of two squares: 2² + 2²

Aliquot sequence: 8 → 7 → 1 → 0 — terminates at zero

Continued fraction of √n

√8 = [2; (1, 4)]

Period length 2 — the block in parentheses repeats forever.

Representations

In words: eight
Ordinal: 8th
Roman numeral: VIII
Binary: 1000
Octal: 10
Hexadecimal: 0x8
Base64: CA==
One's complement: 247 (8-bit)

In other bases

ternary (3) 22

quaternary (4) 20

quinary (5) 13

senary (6) 12

septenary (7) 11

nonary (9) 8

undecimal (11) 8

duodecimal (12) 8

tridecimal (13) 8

tetradecimal (14) 8

pentadecimal (15) 8

Historical numeral systems

Babylonian (base 60): 𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ηʹ
Mayan (base 20): 𝋨
Chinese: 八
Chinese (financial): 捌

In other modern scripts

Eastern Arabic ٨ Devanagari ८ Bengali ৮ Tamil ௮ Thai ๘ Tibetan ༨ Khmer ៨ Lao ໘ Burmese ၈

Digit at this position in famous constants

π — Pi (π): Digit 8 = 6
e — Euler's number (e): Digit 8 = 8
φ — Golden ratio (φ): Digit 8 = 9
√2 — Pythagoras's (√2): Digit 8 = 5
ln 2 — Natural log of 2: Digit 8 = 1
γ — Euler-Mascheroni (γ): Digit 8 = 6

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 8, here are decompositions:

3 + 5 = 8

ASCII character

As an ASCII codepoint, 8 is BS (backspace). ASCII control character.

Hex color

#000008

RGB(0, 0, 8)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.8.

Address: 0.0.0.8
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.8

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

US numbered highway

Matches numbered highway designation:

I-8 — San Diego, CA to Casa Grande, AZ.

Interstate 8 on Wikipedia ↗

Musical pitch

As a MIDI note number, 8 is G♯-1 (13 Hz at concert pitch). (below the ~20 Hz floor of human hearing — likely inaudible)

Atomic number

On the periodic table, atomic number 8 is Oxygen (O) — period 2.

Oxygen on Wikipedia ↗