1,231
1,231 is a prime, odd, a calendar year.
1,231 (one thousand two hundred thirty-one) is an odd 4-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in Roman numerals it is MCCXXXI and in binary, 10011001111.
Interestingness
Historical context — 1231 AD
Calendar year
Year 1231 (MCCXXXI) was a common year starting on Wednesday of the 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
-
Wednesday
January 1, 1231
- Ended on
-
Wednesday
December 31, 1231
- Friday the 13ths
-
1
One Friday the 13th this year.
- Decade
-
1230s
1230–1239
- Century
-
13th century
1201–1300
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
795
795 years before 2026.
In other calendars
- Hebrew
-
4991 / 4992 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
628 / 629 AH
Lunar calendar; year spans differ from Gregorian.
- 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
-
1774 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
609 / 610 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1223 / 1224 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1153 / 1152 Saka
Indian national calendar; year starts in March.
Properties
Primality
1,231 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√1,231 = [35; (11, 1, 2, 7, 2, 4, 1, 13, 4, 1, 1, 1, 1, 6, 2, 2, 4, 3, 1, 2, 23, 35, 23, 2, …)]
Period length 44 — the block in parentheses repeats forever.
Representations
- In words
- one thousand two hundred thirty-one
- Ordinal
- 1231st
- Roman numeral
- MCCXXXI
- Binary
- 10011001111
- Octal
- 2317
- Hexadecimal
- 0x4CF
- Base64
- BM8=
- One's complement
- 64,304 (16-bit)
- Scientific notation
- 1.231 × 10³
- As a duration
- 1,231 s = 20 minutes, 31 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋 𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵ασλαʹ
- Mayan (base 20)
- 𝋣·𝋡·𝋫
- Chinese
- 一千二百三十一
- Chinese (financial)
- 壹仟貳佰參拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,231 = 2
- e — Euler's number (e)
- Digit 1,231 = 7
- φ — Golden ratio (φ)
- Digit 1,231 = 4
- √2 — Pythagoras's (√2)
- Digit 1,231 = 3
- ln 2 — Natural log of 2
- Digit 1,231 = 6
- γ — Euler-Mascheroni (γ)
- Digit 1,231 = 9
Also seen as
UTF-8 encoding: D3 8F (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.4.207.
- Address
- 0.0.4.207
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.4.207
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Heard as a frequency, 1,231 Hz is closest to:
- Concert pitch (A4 = 440 Hz): D♯6 (1244.5 Hz, -19¢)
- Scientific pitch (C4 = 256 Hz): D♯6 (1217.7 Hz, +19¢)
- Baroque pitch (A4 = 415 Hz): E6 (1243.6 Hz, -18¢)
The digit sequence 1231 first appears in π at position 9,450 of the decimal expansion (the 9,450ordinal-suffix:th digit after the integer 3).
Search range: the first 1,000,000 fractional digits of π. Any 6-digit-or-shorter string is virtually guaranteed to appear in there — the more interesting signal is the position.
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.