85
85 is a composite number, odd, a calendar year.
85 (eighty-five) is an odd 2-digit number. It is a composite number with 4 divisors, and factors as 5 × 17. Written other ways, in Roman numerals it is LXXXV and in binary, 1010101.
Interestingness
Historical context — 85 AD
Calendar year
AD 85 (LXXXV) was a common year starting on Saturday of the Julian calendar.
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Historical context — 85 BC
Calendar year
Year 85 BC was a year of the pre-Julian Roman calendar.
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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
- 52
- Started on
-
Monday
January 1, 85
- Ended on
-
Monday
December 31, 85
- 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
-
1,941
1941 years before 2026.
In other calendars
- Hebrew
-
3845 / 3846 AM
Rosh Hashanah falls in September/October.
- 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
-
628 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Ethiopian
-
77 / 78 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
7 / 6 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 5 × 17
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√85 = [9; (4, 1, 1, 4, 18)]
Period length 5 — the block in parentheses repeats forever.
Representations
- In words
- eighty-five
- Ordinal
- 85th
- Roman numeral
- LXXXV
- Binary
- 1010101
- Octal
- 125
- Hexadecimal
- 0x55
- Base64
- VQ==
- One's complement
- 170 (8-bit)
- Scientific notation
- 8.5 × 10¹
- As a duration
- 85 s = 1 minute, 25 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒁹 𒌋𒌋𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- πεʹ
- Mayan (base 20)
- 𝋤·𝋥
- Chinese
- 八十五
- Chinese (financial)
- 捌拾伍
Digit at this position in famous constants
- π — Pi (π)
- Digit 85 = 8
- e — Euler's number (e)
- Digit 85 = 1
- φ — Golden ratio (φ)
- Digit 85 = 7
- √2 — Pythagoras's (√2)
- Digit 85 = 0
- ln 2 — Natural log of 2
- Digit 85 = 5
- γ — Euler-Mascheroni (γ)
- Digit 85 = 6
Also seen as
As an ASCII codepoint, 85 is U. Printable ASCII character U.
As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.85.
- Address
- 0.0.0.85
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.0.85
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Matches numbered highway designation:
- I-85 — Montgomery, AL to Petersburg, VA.
Heard as a frequency, 85 Hz is closest to:
- Concert pitch (A4 = 440 Hz): F2 (87.3 Hz, -46¢ — about midway to E2)
- Scientific pitch (C4 = 256 Hz): F2 (85.4 Hz, -9¢)
- Baroque pitch (A4 = 415 Hz): F♯2 (87.2 Hz, -45¢ — about midway to F2)
As a MIDI note number, 85 is C♯6 (1108.7 Hz at concert pitch).
On the periodic table, atomic number 85 is Astatine (At) — period 6.
Related reading
- Egyptian hieroglyphic numerals — Seven hieroglyphs for every power of ten, from a single stroke to a million.