75
75 is a composite number, odd, a calendar year.
75 (seventy-five) is an odd 2-digit number. It is a composite number with 6 divisors, and factors as 3 × 5². Written other ways, in Roman numerals it is LXXV and in binary, 1001011.
Interestingness
Historical context — 75 AD
Calendar year
AD 75 (LXXV) was a common year starting on Sunday of the Julian calendar.
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Historical context — 75 BC
Calendar year
Year 75 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
-
Tuesday
January 1, 75
- Ended on
-
Tuesday
December 31, 75
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Decade
-
70s
70–79
- Century
-
1st century
1–100
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,951
1951 years before 2026.
In other calendars
- Hebrew
-
3835 / 3836 AM
Rosh Hashanah falls in September/October.
- Chinese
-
Year of the zodiac:Wood zodiac:Pig
Sexagenary cycle position 12 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
618 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Ethiopian
-
67 / 68 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
-3 / -4 Saka
Indian national calendar; year starts in March.
Properties
Primality
Prime factorization: 3 × 5 2
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√75 = [8; (1, 1, 1, 16)]
Period length 4 — the block in parentheses repeats forever.
Representations
- In words
- seventy-five
- Ordinal
- 75th
- Roman numeral
- LXXV
- Binary
- 1001011
- Octal
- 113
- Hexadecimal
- 0x4B
- Base64
- Sw==
- One's complement
- 180 (8-bit)
- Scientific notation
- 7.5 × 10¹
- As a duration
- 75 s = 1 minute, 15 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒁹 𒌋𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- οεʹ
- Mayan (base 20)
- 𝋣·𝋯
- Chinese
- 七十五
- Chinese (financial)
- 柒拾伍
Digit at this position in famous constants
- π — Pi (π)
- Digit 75 = 8
- e — Euler's number (e)
- Digit 75 = 5
- φ — Golden ratio (φ)
- Digit 75 = 1
- √2 — Pythagoras's (√2)
- Digit 75 = 6
- ln 2 — Natural log of 2
- Digit 75 = 6
- γ — Euler-Mascheroni (γ)
- Digit 75 = 7
Also seen as
As an ASCII codepoint, 75 is K. Printable ASCII character K.
As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.75.
- Address
- 0.0.0.75
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.0.75
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Matches numbered highway designation:
- I-75 — Hialeah, FL to Sault Ste. Marie, MI.
Heard as a frequency, 75 Hz is closest to:
- Concert pitch (A4 = 440 Hz): D2 (73.4 Hz, +37¢)
- Scientific pitch (C4 = 256 Hz): D♯2 (76.1 Hz, -25¢)
- Baroque pitch (A4 = 415 Hz): D♯2 (73.4 Hz, +38¢)
As a MIDI note number, 75 is D♯5 (622.3 Hz at concert pitch).
On the periodic table, atomic number 75 is Rhenium (Re) — period 6.
Related reading
- Babylonian numerals — The base-60 cuneiform system that gave us 60 minutes, 60 seconds, and 360°.