Number

19,991

19,991 is a prime, odd.

Arithmetic Number Chen Prime Deficient Number Evil Number Flippable Palindrome Prime Sexy Prime Sophie Germain Prime Squarefree Twin Prime

Properties

Parity: Odd
Digit count: 5
Digit sum: 29
Digit product: 729
Digital root: 2
Palindrome: Yes
Bit width: 15 bits
Flips to (rotate 180°): 16,661
Square (n²): 399,640,081
Cube (n³): 7,989,204,859,271
Divisor count: 2
σ(n) — sum of divisors: 19,992
φ(n) — Euler's totient: 19,990

Primality

19,991 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 19991

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 19,991)

1 × 19991

First multiples

19,991 · 39,982 (double) · 59,973 · 79,964 · 99,955 · 119,946 · 139,937 · 159,928 · 179,919 · 199,910

Sums & aliquot sequence

As consecutive integers: 9,995 + 9,996

Representations

In words: nineteen thousand nine hundred ninety-one
Ordinal: 19991st
Binary: 100111000010111
Octal: 47027
Hexadecimal: 0x4E17
Base64: Thc=
One's complement: 45,544 (16-bit)

In other bases

ternary (3) 1000102102

quaternary (4) 10320113

quinary (5) 1114431

senary (6) 232315

septenary (7) 112166

nonary (9) 30372

undecimal (11) 14024

duodecimal (12) b69b

tridecimal (13) 913a

tetradecimal (14) 73dd

pentadecimal (15) 5dcb

Historical numeral systems

Babylonian (base 60): 𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒁹𒁹𒁹 𒌋𒁹
Egyptian hieroglyphic: 𓂍𓆼𓆼𓆼𓆼𓆼𓆼𓆼𓆼𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
Greek (Milesian): ͵ιθϡϟαʹ
Mayan (base 20): 𝋢·𝋩·𝋳·𝋫
Chinese: 一萬九千九百九十一
Chinese (financial): 壹萬玖仟玖佰玖拾壹

In other modern scripts

Eastern Arabic ١٩٩٩١ Devanagari १९९९१ Bengali ১৯৯৯১ Tamil ௧௯௯௯௧ Thai ๑๙๙๙๑ Tibetan ༡༩༩༩༡ Khmer ១៩៩៩១ Lao ໑໙໙໙໑ Burmese ၁၉၉၉၁

Digit at this position in famous constants

π — Pi (π): Digit 19,991 = 4
e — Euler's number (e): Digit 19,991 = 2
φ — Golden ratio (φ): Digit 19,991 = 6
√2 — Pythagoras's (√2): Digit 19,991 = 6
ln 2 — Natural log of 2: Digit 19,991 = 7
γ — Euler-Mascheroni (γ): Digit 19,991 = 1

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 19,979 (gap of 12)
Next prime: 19,993 (gap of 2)

Pair status: twin with 19993.

Unicode codepoint

丗

CJK Unified Ideograph-4E17

U+4E17

Other letter (Lo)

UTF-8 encoding: E4 B8 97 (3 bytes).

Lookup U+4E17 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#004E17

RGB(0, 78, 23)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.78.23.

Address: 0.0.78.23
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.78.23

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

Position in π

The digit sequence 19991 first appears in π at position 42,058 of the decimal expansion (the 42,058ordinal-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 19991 on Pi Search ↗