Number

13,781

13,781 is a prime, odd.

13,781 (thirteen thousand seven hundred eighty-one) is an odd 5-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in hexadecimal, 0x35D5.

Arithmetic Number Cube-Free Deficient Number Emirp Odious Number Prime Pythagorean Prime Recamán's Sequence Squarefree

Interestingness

★ ★ ★ ★ ☆

7 notable facts · grade B

13,769 13,770 13,771 13,772 13,773 13,774 13,775 13,776 13,777 13,778 13,779 13,780 13,781 13,782 13,783 13,784 13,785 13,786 13,787 13,788 13,789 13,790 13,791 13,792 13,793

less more

Properties

Parity: Odd
Digit count: 5
Digit sum: 20
Digit product: 168
Digital root: 2
Palindrome: No
Bit width: 14 bits
Reversed: 18,731
Recamán's sequence: a(21,154) = 13,781
Square (n²): 189,915,961
Cube (n³): 2,617,231,858,541
Divisor count: 2
σ(n) — sum of divisors: 13,782
φ(n) — Euler's totient: 13,780

Primality

13,781 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 13781

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 13,781)

1 × 13781

First multiples

13,781 · 27,562 (double) · 41,343 · 55,124 · 68,905 · 82,686 · 96,467 · 110,248 · 124,029 · 137,810

Sums & aliquot sequence

As a sum of two squares: 41² + 110²

As consecutive integers: 6,890 + 6,891

Continued fraction of √n

√13,781 = [117; (2, 1, 1, 4, 1, 2, 1, 3, 1, 3, 2, 11, 1, 10, 1, 4, 1, 1, 5, 5, 1, 1, 4, 1, …)]

Period length 39 — the block in parentheses repeats forever.

Representations

In words: thirteen thousand seven hundred eighty-one
Ordinal: 13781st
Binary: 11010111010101
Octal: 32725
Hexadecimal: 0x35D5
Base64: NdU=
One's complement: 51,754 (16-bit)
Scientific notation: 1.3781 × 10⁴
As a duration: 13,781 s = 3 hours, 49 minutes, 41 seconds

In other bases

ternary (3) 200220102

quaternary (4) 3113111

quinary (5) 420111

senary (6) 143445

septenary (7) 55115

nonary (9) 20812

undecimal (11) a399

duodecimal (12) 7b85

tridecimal (13) 6371

tetradecimal (14) 5045

pentadecimal (15) 413b

As an angle

13,781° = 38 × 360° + 101°

101° ≈ 1.763 rad

Compass bearing: E (east)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
Egyptian hieroglyphic: 𓂍𓆼𓆼𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): ͵ιγψπαʹ
Mayan (base 20): 𝋡·𝋮·𝋩·𝋡
Chinese: 一萬三千七百八十一
Chinese (financial): 壹萬參仟柒佰捌拾壹

In other modern scripts

Eastern Arabic ١٣٧٨١ Devanagari १३७८१ Bengali ১৩৭৮১ Tamil ௧௩௭௮௧ Thai ๑๓๗๘๑ Tibetan ༡༣༧༨༡ Khmer ១៣៧៨១ Lao ໑໓໗໘໑ Burmese ၁၃၇၈၁

Digit at this position in famous constants

π — Pi (π): Digit 13,781 = 7
e — Euler's number (e): Digit 13,781 = 2
φ — Golden ratio (φ): Digit 13,781 = 1
√2 — Pythagoras's (√2): Digit 13,781 = 6
ln 2 — Natural log of 2: Digit 13,781 = 0
γ — Euler-Mascheroni (γ): Digit 13,781 = 5

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 13,763 (gap of 18)
Next prime: 13,789 (gap of 8)

Unicode codepoint

㗕

CJK Unified Ideograph-35D5

U+35D5

Other letter (Lo)

UTF-8 encoding: E3 97 95 (3 bytes).

Lookup U+35D5 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#0035D5

RGB(0, 53, 213)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.53.213.

Address: 0.0.53.213
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.53.213

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

Musical pitch

Heard as a frequency, 13,781 Hz is closest to:

Concert pitch (A4 = 440 Hz): A9 (14080 Hz, -37¢)
Scientific pitch (C4 = 256 Hz): A9 (13777.2 Hz, exact)
Baroque pitch (A4 = 415 Hz): A♯9 (14069.7 Hz, -36¢)

Position in π

The digit sequence 13781 first appears in π at position 16,248 of the decimal expansion (the 16,248ordinal-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 13781 on Pi Search ↗