Number

31,991

31,991 is a prime, odd.

31,991 (thirty-one thousand nine hundred ninety-one) is an odd 5-digit number. It is a prime number — divisible only by 1 and itself. Written other ways, in hexadecimal, 0x7CF7.

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

Interestingness

★ ★ ★ ★ ☆

6 notable facts · grade B

31,979 31,980 31,981 31,982 31,983 31,984 31,985 31,986 31,987 31,988 31,989 31,990 31,991 31,992 31,993 31,994 31,995 31,996 31,997 31,998 31,999 32,000 32,001 32,002 32,003

less more

Properties

Parity: Odd
Digit count: 5
Digit sum: 23
Digit product: 243
Digital root: 5
Palindrome: No
Bit width: 15 bits
Reversed: 19,913
Recamán's sequence: a(13,353) = 31,991
Square (n²): 1,023,424,081
Cube (n³): 32,740,359,775,271
Divisor count: 2
σ(n) — sum of divisors: 31,992
φ(n) — Euler's totient: 31,990

Primality

31,991 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 31991

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 31,991)

1 × 31991

First multiples

31,991 · 63,982 (double) · 95,973 · 127,964 · 159,955 · 191,946 · 223,937 · 255,928 · 287,919 · 319,910

Sums & aliquot sequence

As consecutive integers: 15,995 + 15,996

Continued fraction of √n

√31,991 = [178; (1, 6, 6, 2, 1, 3, 2, 1, 50, 2, 2, 4, 4, 12, 10, 7, 4, 1, 31, 1, 2, 1, 1, 70, …)]

Representations

In words: thirty-one thousand nine hundred ninety-one
Ordinal: 31991st
Binary: 111110011110111
Octal: 76367
Hexadecimal: 0x7CF7
Base64: fPc=
One's complement: 33,544 (16-bit)
Scientific notation: 3.1991 × 10⁴
As a duration: 31,991 s = 8 hours, 53 minutes, 11 seconds

In other bases

ternary (3) 1121212212

quaternary (4) 13303313

quinary (5) 2010431

senary (6) 404035

septenary (7) 162161

nonary (9) 47785

undecimal (11) 22043

duodecimal (12) 1661b

tridecimal (13) 1173b

tetradecimal (14) b931

pentadecimal (15) 972b

Palindromic in base 8

As an angle

31,991° = 88 × 360° + 311°

311° ≈ 5.428 rad

Compass bearing: NW (northwest)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒌋𒁹𒁹𒁹 𒌋𒁹
Egyptian hieroglyphic: 𓂍𓂍𓂍𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): ͵λαϡϟαʹ
Mayan (base 20): 𝋣·𝋳·𝋳·𝋫
Chinese: 三萬一千九百九十一
Chinese (financial): 參萬壹仟玖佰玖拾壹

In other modern scripts

Eastern Arabic ٣١٩٩١ Devanagari ३१९९१ Bengali ৩১৯৯১ Tamil ௩௧௯௯௧ Thai ๓๑๙๙๑ Tibetan ༣༡༩༩༡ Khmer ៣១៩៩១ Lao ໓໑໙໙໑ Burmese ၃၁၉၉၁

Digit at this position in famous constants

π — Pi (π): Digit 31,991 = 2
e — Euler's number (e): Digit 31,991 = 1
φ — Golden ratio (φ): Digit 31,991 = 0
√2 — Pythagoras's (√2): Digit 31,991 = 0
ln 2 — Natural log of 2: Digit 31,991 = 1
γ — Euler-Mascheroni (γ): Digit 31,991 = 4

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 31,981 (gap of 10)
Next prime: 32,003 (gap of 12)

Unicode codepoint

糷

CJK Unified Ideograph-7Cf7

U+7CF7

Other letter (Lo)

UTF-8 encoding: E7 B3 B7 (3 bytes).

Lookup U+7CF7 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#007CF7

RGB(0, 124, 247)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.124.247.

Address: 0.0.124.247
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.124.247

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

Position in π

The digit sequence 31991 first appears in π at position 144,937 of the decimal expansion (the 144,937ordinal-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 31991 on Pi Search ↗