Number
21,991
21,991 is a prime, odd.
Properties
- Parity
- Odd
- Digit count
- 5
- Digit sum
- 22
- Digit product
- 162
- Digital root
- 4
- Palindrome
- No
- Bit width
- 15 bits
- Reversed
- 19,912
- Recamán's sequence
- a(167,781) = 21,991
- Square (n²)
- 483,604,081
- Cube (n³)
- 10,634,937,345,271
- Divisor count
- 2
- σ(n) — sum of divisors
- 21,992
- φ(n) — Euler's totient
- 21,990
Primality
21,991 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Aliquot sum (sum of proper divisors):
1
First multiples
21,991
·
43,982
(double)
·
65,973
·
87,964
·
109,955
·
131,946
·
153,937
·
175,928
·
197,919
·
219,910
Sums & aliquot sequence
As consecutive integers:
10,995 + 10,996
Representations
- In words
- twenty-one thousand nine hundred ninety-one
- Ordinal
- 21991st
- Binary
- 101010111100111
- Octal
- 52747
- Hexadecimal
- 0x55E7
- Base64
- Vec=
- One's complement
- 43,544 (16-bit)
In other bases
ternary (3)
1010011111
quaternary (4)
11113213
quinary (5)
1200431
senary (6)
245451
septenary (7)
121054
nonary (9)
33144
undecimal (11)
15582
duodecimal (12)
10887
tridecimal (13)
a018
tetradecimal (14)
802b
pentadecimal (15)
67b1
Historical numeral systems
- Babylonian (base 60)
- 𒁹𒁹𒁹𒁹𒁹𒁹 𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓂍𓂍𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵καϡϟαʹ
- Mayan (base 20)
- 𝋢·𝋮·𝋳·𝋫
- Chinese
- 二萬一千九百九十一
- Chinese (financial)
- 貳萬壹仟玖佰玖拾壹
In other modern scripts
Eastern Arabic
٢١٩٩١
Devanagari
२१९९१
Bengali
২১৯৯১
Tamil
௨௧௯௯௧
Thai
๒๑๙๙๑
Tibetan
༢༡༩༩༡
Khmer
២១៩៩១
Lao
໒໑໙໙໑
Burmese
၂၁၉၉၁
Digit at this position in famous constants
- π — Pi (π)
- Digit 21,991 = 6
- e — Euler's number (e)
- Digit 21,991 = 5
- φ — Golden ratio (φ)
- Digit 21,991 = 9
- √2 — Pythagoras's (√2)
- Digit 21,991 = 2
- ln 2 — Natural log of 2
- Digit 21,991 = 7
- γ — Euler-Mascheroni (γ)
- Digit 21,991 = 5
Also seen as
Prime neighborhood
Unicode codepoint
嗧
CJK Unified Ideograph-55E7
U+55E7
Other letter (Lo)
UTF-8 encoding: E5 97 A7 (3 bytes).
Hex color
#0055E7
RGB(0, 85, 231)
IPv4 address
As an unsigned 32-bit integer, this is the IPv4 address 0.0.85.231.
- Address
- 0.0.85.231
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.85.231
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Position in π
The digit sequence 21991 first appears in π at position 49,318 of the decimal expansion (the 49,318ordinal-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.