1,291
1,291 is a prime, odd, a calendar year.
1,291 (one thousand two hundred ninety-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 MCCXCI and in binary, 10100001011.
Interestingness
Notable events — 1291 AD
- May 18 Mamluk forces capture Acre, ending the last Crusader stronghold in the Levant.
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
- 52
- Started on
-
Monday
January 1, 1291
- Ended on
-
Monday
December 31, 1291
- Friday the 13ths
-
2
2 Friday the 13ths this year.
- Decade
-
1290s
1290–1299
- Century
-
13th century
1201–1300
- Millennium
-
2nd millennium
1001–2000
- Years ago
-
735
735 years before 2026.
In other calendars
- Hebrew
-
5051 / 5052 AM
Rosh Hashanah falls in September/October.
- Islamic Hijri
-
689 / 691 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
-
1834 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
- Persian Solar Hijri
-
669 / 670 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
- Ethiopian
-
1283 / 1284 ET
Year boundary at Enkutatash (September 11/12).
- Indian National (Saka)
-
1213 / 1212 Saka
Indian national calendar; year starts in March.
Properties
Primality
1,291 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√1,291 = [35; (1, 13, 2, 1, 1, 2, 3, 1, 1, 1, 1, 4, 1, 11, 6, 2, 4, 3, 23, 1, 1, 1, 4, 7, …)]
Representations
- In words
- one thousand two hundred ninety-one
- Ordinal
- 1291st
- Roman numeral
- MCCXCI
- Binary
- 10100001011
- Octal
- 2413
- Hexadecimal
- 0x50B
- Base64
- BQs=
- One's complement
- 64,244 (16-bit)
- Scientific notation
- 1.291 × 10³
- As a duration
- 1,291 s = 21 minutes, 31 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒁹 𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵ασϟαʹ
- Mayan (base 20)
- 𝋣·𝋤·𝋫
- Chinese
- 一千二百九十一
- Chinese (financial)
- 壹仟貳佰玖拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 1,291 = 4
- e — Euler's number (e)
- Digit 1,291 = 1
- φ — Golden ratio (φ)
- Digit 1,291 = 4
- √2 — Pythagoras's (√2)
- Digit 1,291 = 8
- ln 2 — Natural log of 2
- Digit 1,291 = 2
- γ — Euler-Mascheroni (γ)
- Digit 1,291 = 7
Also seen as
UTF-8 encoding: D4 8B (2 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.5.11.
- Address
- 0.0.5.11
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.5.11
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Heard as a frequency, 1,291 Hz is closest to:
- Concert pitch (A4 = 440 Hz): E6 (1318.5 Hz, -37¢)
- Scientific pitch (C4 = 256 Hz): E6 (1290.2 Hz, +1¢)
- Baroque pitch (A4 = 415 Hz): F6 (1317.5 Hz, -35¢)
The digit sequence 1291 first appears in π at position 7,876 of the decimal expansion (the 7,876ordinal-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.