331
331 is a prime, odd, a calendar year.
331 (three hundred thirty-one) is an odd 3-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in Roman numerals it is CCCXXXI and in binary, 101001011.
Interestingness
Historical context — 331 AD
Calendar year
Year 331 (CCCXXXI) was a common year starting on Friday of the Julian calendar.
Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →
Notable events — 331 BC
- Oct 1 Alexander decisively defeats Darius III at Gaugamela, breaking the Persian Empire.
Events compiled from Wikipedia ↗ · Licensed CC BY-SA 4.0
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
-
53
Long year: contains 53 ISO weeks.
- Started on
-
Thursday
January 1, 331
- Ended on
-
Thursday
December 31, 331
- Friday the 13ths
-
3
3 Friday the 13ths this year.
- Decade
-
330s
330–339
- Century
-
4th century
301–400
- Millennium
-
1st millennium
1–1000
- Years ago
-
1,695
1695 years before 2026.
In other calendars
- Hebrew
-
4091 / 4092 AM
Rosh Hashanah falls in September/October.
- Chinese
-
Year of the zodiac:Metal zodiac:Rabbit
Sexagenary cycle position 28 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
874 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Ethiopian
-
323 / 324 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
253 / 252 Saka
Indian national calendar; year starts in March.
Properties
Primality
331 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√331 = [18; (5, 5, 1, 6, 2, 3, 1, 1, 2, 1, 2, 1, 11, 2, 1, 1, 17, 1, 1, 2, 11, 1, 2, 1, …)]
Period length 34 — the block in parentheses repeats forever.
Representations
- In words
- three hundred thirty-one
- Ordinal
- 331st
- Roman numeral
- CCCXXXI
- Binary
- 101001011
- Octal
- 513
- Hexadecimal
- 0x14B
- Base64
- AUs=
- One's complement
- 65,204 (16-bit)
- Scientific notation
- 3.31 × 10²
- As a duration
- 331 s = 5 minutes, 31 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓍢𓍢𓍢𓎆𓎆𓎆𓏺
- Greek (Milesian)
- τλαʹ
- Mayan (base 20)
- 𝋰·𝋫
- Chinese
- 三百三十一
- Chinese (financial)
- 參佰參拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 331 = 0
- e — Euler's number (e)
- Digit 331 = 0
- φ — Golden ratio (φ)
- Digit 331 = 5
- √2 — Pythagoras's (√2)
- Digit 331 = 5
- ln 2 — Natural log of 2
- Digit 331 = 4
- γ — Euler-Mascheroni (γ)
- Digit 331 = 0
Also seen as
UTF-8 encoding: C5 8B (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.1.75.
- Address
- 0.0.1.75
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.1.75
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The number 331 is an active NANP area code (North American Numbering Plan).
- Primary area
- Western suburbs of Chicago
- Region
- Illinois
- Country
- United States
Most NANP area codes have multiple overlays in dense regions; the primary area listed is the historic/largest population center for this code.
Heard as a frequency, 331 Hz is closest to:
- Concert pitch (A4 = 440 Hz): E4 (329.6 Hz, +7¢)
- Scientific pitch (C4 = 256 Hz): E4 (322.5 Hz, +45¢ — about midway to F4)
- Baroque pitch (A4 = 415 Hz): F4 (329.4 Hz, +8¢)
On an ingredients label, E331 is Sodium citrates, an antioxidant or acidity regulator.
Related reading
- Prime numbers — The building blocks of arithmetic: what primes are, why they matter, and how we find them.
- Egyptian hieroglyphic numerals — Seven hieroglyphs for every power of ten, from a single stroke to a million.