17
17 is a prime, odd, a calendar year.
Seventeen is the seventh prime, and is famously the favorite ‘random’ number people pick when asked. It is the only prime that is the sum of four consecutive primes (2 + 3 + 5 + 7).
Interestingness
Historical context — 17 AD
Calendar year
AD 17 (XVII) was a common year starting on Friday of the Julian calendar.
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Historical context — 17 BC
Calendar year
Year 17 BC was either a common year starting on Sunday or Monday or a leap year starting on Saturday, Sunday or Monday of the Julian calendar and a leap year starting on Friday of the Proleptic Julian 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
-
Sunday
January 1, 17
- Ended on
-
Sunday
December 31, 17
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Decade
-
10s
10–19
- Century
-
1st century
1–100
- Millennium
-
1st millennium
1–1000
- Years ago
-
2,009
2009 years before 2026.
In other calendars
- Hebrew
-
3777 / 3778 AM
Rosh Hashanah falls in September/October.
- Chinese
-
Year of the zodiac:Fire zodiac:Ox
Sexagenary cycle position 14 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
560 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Ethiopian
-
9 / 10 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
-61 / -62 Saka
Indian national calendar; year starts in March.
Cultural significance
Avoided — many Italian airlines skip row 17.
The Roman numeral XVII is an anagram of VIXI — Latin for "I have lived," implying death.
Sourced from Wikipedia (Numerology, Chinese numerology, Gematria, and per-culture articles).
Properties
Primality
17 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√17 = [4; (8)]
Period length 1 — the block in parentheses repeats forever.
Representations
- In words
- seventeen
- Ordinal
- 17th
- Roman numeral
- XVII
- Binary
- 10001
- Octal
- 21
- Hexadecimal
- 0x11
- Base64
- EQ==
- One's complement
- 238 (8-bit)
- Scientific notation
- 1.7 × 10¹
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹
- Egyptian hieroglyphic
- 𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺
- Greek (Milesian)
- ιζʹ
- Mayan (base 20)
- 𝋱
- Chinese
- 一十七
- Chinese (financial)
- 壹拾柒
Digit at this position in famous constants
- π — Pi (π)
- Digit 17 = 2
- e — Euler's number (e)
- Digit 17 = 2
- φ — Golden ratio (φ)
- Digit 17 = 8
- √2 — Pythagoras's (√2)
- Digit 17 = 0
- ln 2 — Natural log of 2
- Digit 17 = 3
- γ — Euler-Mascheroni (γ)
- Digit 17 = 8
Also seen as
As an ASCII codepoint, 17 is control character (0x11). ASCII control character.
As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.17.
- Address
- 0.0.0.17
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.0.17
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Matches numbered highway designation:
- I-17 — Phoenix to Flagstaff, AZ.
Heard as a frequency, 17 Hz is closest to:
- Concert pitch (A4 = 440 Hz): C♯0 (17.3 Hz, -33¢)
- Scientific pitch (C4 = 256 Hz): C♯0 (17 Hz, +5¢)
- Baroque pitch (A4 = 415 Hz): D0 (17.3 Hz, -31¢)
As a MIDI note number, 17 is F0 (21.8 Hz at concert pitch). (very low — many laptop and phone speakers can't reproduce it)
On the periodic table, atomic number 17 is Chlorine (Cl) — period 3.
Related reading
- Prime numbers — The building blocks of arithmetic: what primes are, why they matter, and how we find them.
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros.