number.wiki

Number

80

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

Abundant Number Evil Number Flippable Harshad / Niven Pernicious Number Practical Number Recamán's Sequence Semiperfect Number Year

Historical context — 80 AD

Calendar year

AD 80 (LXXX) was a leap year starting on Saturday of the Julian calendar.

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

Historical context — 80 BC

Calendar year

Year 80 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 · English fallback 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: Monday
January 1, 80
Ended on: Tuesday
December 31, 80
Friday the 13ths: 2
2 Friday the 13ths this year.
Decade: 80s
80–89
Century: 1st century
1–100
Millennium: 1st millennium
1–1000
Years ago: 1,946
1946 years before 2026.

In other calendars

Hebrew: 3840 / 3841 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Metal zodiac:Dragon
Sexagenary cycle position 17 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 623 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 72 / 73 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 2 / 1 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 2
Digit sum: 8
Digit product: 0
Digital root: 8
Palindrome: No
Bit width: 7 bits
Reversed: 8
Flips to (rotate 180°): 8
Recamán's sequence: a(43) = 80
Square (n²): 6,400
Cube (n³): 512,000
Divisor count: 10
σ(n) — sum of divisors: 186
φ(n) — Euler's totient: 32
Sum of prime factors: 13

Primality

Prime factorization: 2 ⁴ × 5

Nearest primes: 79 (−1) · 83 (+3)

Divisors & multiples

All divisors (10)

1 · 2 · 4 · 5 · 8 · 10 · 16 · 20 · 40 (half) · 80

Aliquot sum (sum of proper divisors): 106

Factor pairs (a × b = 80)

1 × 80

2 × 40

4 × 20

5 × 16

8 × 10

First multiples

80 · 160 (double) · 240 · 320 · 400 · 480 · 560 · 640 · 720 · 800

Sums & aliquot sequence

As a sum of two squares: 4² + 8²

As consecutive integers: 14 + 15 + 16 + 17 + 18

Aliquot sequence: 80 → 106 → 56 → 64 → 63 → 41 → 1 → 0 — terminates at zero

Representations

In words: eighty
Ordinal: 80th
Roman numeral: LXXX
Binary: 1010000
Octal: 120
Hexadecimal: 0x50
Base64: UA==
One's complement: 175 (8-bit)

In other bases

ternary (3) 2222

quaternary (4) 1100

quinary (5) 310

senary (6) 212

septenary (7) 143

nonary (9) 88

undecimal (11) 73

duodecimal (12) 68

tridecimal (13) 62

tetradecimal (14) 5a

pentadecimal (15) 55

Historical numeral systems

Babylonian (base 60): 𒁹 𒌋𒌋
Egyptian hieroglyphic: 𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆
Greek (Milesian): πʹ
Mayan (base 20): 𝋤·𝋠
Chinese: 八十
Chinese (financial): 捌拾

In other modern scripts

Eastern Arabic ٨٠ Devanagari ८० Bengali ৮০ Tamil ௮௦ Thai ๘๐ Tibetan ༨༠ Khmer ៨០ Lao ໘໐ Burmese ၈၀

Digit at this position in famous constants

π — Pi (π): Digit 80 = 9
e — Euler's number (e): Digit 80 = 5
φ — Golden ratio (φ): Digit 80 = 4
√2 — Pythagoras's (√2): Digit 80 = 0
ln 2 — Natural log of 2: Digit 80 = 7
γ — Euler-Mascheroni (γ): Digit 80 = 6

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 80, here are decompositions:

7 + 73 = 80
13 + 67 = 80
19 + 61 = 80
37 + 43 = 80

ASCII character

As an ASCII codepoint, 80 is P. Printable ASCII character P.

Network port

TCP/UDP port 80 is the well-known port for HTTP — HyperText Transfer Protocol — the web.

Hex color

#000050

RGB(0, 0, 80)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.80.

Address: 0.0.0.80
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.80

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

US numbered highway

Matches numbered highway designation:

I-80 — San Francisco, CA to Teaneck, NJ — the longest northern coast-to-coast.

Interstate 80 on Wikipedia ↗