1,931
1,931 is a prime, odd, a calendar year.
1,931 (one thousand nine 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 MCMXXXI and in binary, 11110001011.
Interestingness
Notable events — 1931 AD
- May 1 The Empire State Building opens in New York City.
- Apr 14 Spain proclaims the Second Republic; King Alfonso XIII abdicates.
- Sep 18 Japan invades Manchuria after the staged Mukden Incident.
- Oct 17 Al Capone is convicted of tax evasion.
- Dec 11 The Statute of Westminster grants legislative independence to British Dominions.
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, 1931
- Ended on
-
Thursday
December 31, 1931
- Friday the 13ths
-
3
3 Friday the 13ths this year.
- Easter Sunday
-
April 5
Sunday, April 5, 1931
- Decade
-
1930s
1930–1939
- Century
-
20th century
1901–2000
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
95
95 years before 2026.
In other calendars
- Hebrew
-
5691 / 5692 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
1349 / 1350 AH
Lunar calendar; year spans differ from Gregorian.
- Chinese
-
Year of the zodiac:Metal zodiac:Goat
Sexagenary cycle position 8 of 60. Lunar new year falls in late January / mid-February.
- Buddhist Era
-
2474 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
1309 / 1310 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1923 / 1924 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1853 / 1852 Saka
Indian national calendar; year starts in March.
- Japanese
-
Shōwa 6
Reign-era counting from the start of each emperor's reign.
Properties
Primality
1,931 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√1,931 = [43; (1, 16, 1, 1, 2, 3, 8, 2, 43, 2, 8, 3, 2, 1, 1, 16, 1, 86)]
Period length 18 — the block in parentheses repeats forever.
Representations
- In words
- one thousand nine hundred thirty-one
- Ordinal
- 1931st
- Roman numeral
- MCMXXXI
- Binary
- 11110001011
- Octal
- 3613
- Hexadecimal
- 0x78B
- Base64
- B4s=
- One's complement
- 63,604 (16-bit)
- Scientific notation
- 1.931 × 10³
- As a duration
- 1,931 s = 32 minutes, 11 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒌋𒁹𒁹 𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵αϡλαʹ
- Mayan (base 20)
- 𝋤·𝋰·𝋫
- Chinese
- 一千九百三十一
- Chinese (financial)
- 壹仟玖佰參拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,931 = 7
- e — Euler's number (e)
- Digit 1,931 = 4
- φ — Golden ratio (φ)
- Digit 1,931 = 4
- √2 — Pythagoras's (√2)
- Digit 1,931 = 1
- ln 2 — Natural log of 2
- Digit 1,931 = 9
- γ — Euler-Mascheroni (γ)
- Digit 1,931 = 2
Also seen as
UTF-8 encoding: DE 8B (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.7.139.
- Address
- 0.0.7.139
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.7.139
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Heard as a frequency, 1,931 Hz is closest to:
- Concert pitch (A4 = 440 Hz): B6 (1975.5 Hz, -39¢)
- Scientific pitch (C4 = 256 Hz): B6 (1933.1 Hz, -2¢)
- Baroque pitch (A4 = 415 Hz): C7 (1974.1 Hz, -38¢)
The digit sequence 1931 first appears in π at position 843 of the decimal expansion (the 843ordinal-suffix:rd 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.
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros.