Number

1,391

1,391 is a composite number, odd, a calendar year.

1,391 (one thousand three hundred ninety-one) is an odd 4-digit number. It is a composite number with 4 divisors, and factors as 13 × 107. Written other ways, in Roman numerals it is MCCCXCI and in binary, 10101101111.

Arithmetic Number Cube-Free Deficient Number Evil Number Recamán's Sequence Semiprime Squarefree Year

Interestingness

★ ★ ★ ☆ ☆

5 notable facts · grade C

1,379 1,380 1,381 1,382 1,383 1,384 1,385 1,386 1,387 1,388 1,389 1,390 1,391 1,392 1,393 1,394 1,395 1,396 1,397 1,398 1,399 1,400 1,401 1,402 1,403

less more

Historical context — 1391 AD

Calendar year

Year 1391 (MCCCXCI) was a common year starting on Sunday of the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

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: Saturday
January 1, 1391
Ended on: Saturday
December 31, 1391
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 1390s
1390–1399
Century: 14th century
1301–1400
Millennium: 2nd millennium
1001–2000
Years ago: 635
635 years before 2026.

In other calendars

Hebrew: 5151 / 5152 AM
Rosh Hashanah falls in September/October.
Islamic Hijri: 793 / 794 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: 1934 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Persian Solar Hijri: 769 / 770 SH
Iranian calendar; Nowruz (new year) falls on the spring equinox.
Ethiopian: 1383 / 1384 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 1313 / 1312 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 4
Digit sum: 14
Digit product: 27
Digital root: 5
Palindrome: No
Bit width: 11 bits
Reversed: 1,931
Recamán's sequence: a(8,346) = 1,391
Square (n²): 1,934,881
Cube (n³): 2,691,419,471
Divisor count: 4
σ(n) — sum of divisors: 1,512
φ(n) — Euler's totient: 1,272
Sum of prime factors: 120

Primality

Prime factorization: 13 × 107

Nearest primes: 1,381 (−10) · 1,399 (+8)

Divisors & multiples

All divisors (4)

1 · 13 · 107 · 1391

Aliquot sum (sum of proper divisors): 121

Factor pairs (a × b = 1,391)

1 × 1391

13 × 107

First multiples

1,391 · 2,782 (double) · 4,173 · 5,564 · 6,955 · 8,346 · 9,737 · 11,128 · 12,519 · 13,910

Sums & aliquot sequence

As consecutive integers: 695 + 696 101 + 102 + … + 113 41 + 42 + … + 66

Aliquot sequence: 1,391 → 121 → 12 → 16 → 15 → 9 → 4 → 3 → 1 → 0 — terminates at zero

Continued fraction of √n

√1,391 = [37; (3, 2, 1, 1, 1, 6, 1, 4, 1, 6, 1, 1, 1, 2, 3, 74)]

Period length 16 — the block in parentheses repeats forever.

Representations

In words: one thousand three hundred ninety-one
Ordinal: 1391st
Roman numeral: MCCCXCI
Binary: 10101101111
Octal: 2557
Hexadecimal: 0x56F
Base64: BW8=
One's complement: 64,144 (16-bit)
Scientific notation: 1.391 × 10³
As a duration: 1,391 s = 23 minutes, 11 seconds

In other bases

ternary (3) 1220112

quaternary (4) 111233

quinary (5) 21031

senary (6) 10235

septenary (7) 4025

nonary (9) 1815

undecimal (11) 1055

duodecimal (12) 97b

tridecimal (13) 830

tetradecimal (14) 715

pentadecimal (15) 62b

As an angle

1,391° = 3 × 360° + 311°

311° ≈ 5.428 rad

Compass bearing: NW (northwest)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒌋𒌋𒁹𒁹𒁹 𒌋𒁹
Egyptian hieroglyphic: 𓆼𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): ͵ατϟαʹ
Mayan (base 20): 𝋣·𝋩·𝋫
Chinese: 一千三百九十一
Chinese (financial): 壹仟參佰玖拾壹

In other modern scripts

Eastern Arabic ١٣٩١ Devanagari १३९१ Bengali ১৩৯১ Tamil ௧௩௯௧ Thai ๑๓๙๑ Tibetan ༡༣༩༡ Khmer ១៣៩១ Lao ໑໓໙໑ Burmese ၁၃၉၁

Digit at this position in famous constants

π — Pi (π): Digit 1,391 = 6
e — Euler's number (e): Digit 1,391 = 4
φ — Golden ratio (φ): Digit 1,391 = 1
√2 — Pythagoras's (√2): Digit 1,391 = 2
ln 2 — Natural log of 2: Digit 1,391 = 3
γ — Euler-Mascheroni (γ): Digit 1,391 = 2

Also seen as

Unicode codepoint

Armenian Small Letter Ken

U+056F

Lowercase letter (Ll)

UTF-8 encoding: D5 AF (2 bytes).

Lookup U+056F on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#00056F

RGB(0, 5, 111)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.5.111.

Address: 0.0.5.111
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.5.111

Unspecified address (0.0.0.0/8) — "this network" placeholder.

Musical pitch

Heard as a frequency, 1,391 Hz is closest to:

Concert pitch (A4 = 440 Hz): F6 (1396.9 Hz, -7¢)
Scientific pitch (C4 = 256 Hz): F6 (1366.9 Hz, +30¢)
Baroque pitch (A4 = 415 Hz): F♯6 (1395.9 Hz, -6¢)

Position in π

The digit sequence 1391 first appears in π at position 23,757 of the decimal expansion (the 23,757ordinal-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.

Look up 1391 on Pi Search ↗