21,800
21,800 is a composite number, even.
21,800 (twenty-one thousand eight hundred) is an even 5-digit number. It is a composite number with 24 divisors, and factors as 2³ × 5² × 109. Its proper divisors sum to 29,350, more than the number itself, making it an abundant number. Written other ways, in hexadecimal, 0x5528.
Interestingness
Properties
- Parity
- Even
- Digit count
- 5
- Digit sum
- 11
- Digit product
- 0
- Digital root
- 2
- Palindrome
- No
- Bit width
- 15 bits
- Reversed
- 812
- Recamán's sequence
- a(40,239) = 21,800
- Square (n²)
- 475,240,000
- Cube (n³)
- 10,360,232,000,000
- Divisor count
- 24
- σ(n) — sum of divisors
- 51,150
- φ(n) — Euler's totient
- 8,640
- Sum of prime factors
- 125
Primality
Prime factorization: 2 3 × 5 2 × 109
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√21,800 = [147; (1, 1, 1, 5, 2, 1, 3, 2, 9, 11, 1, 2, 2, 2, 73, 2, 2, 2, 1, 11, 9, 2, 3, 1, …)]
Period length 30 — the block in parentheses repeats forever.
Representations
- In words
- twenty-one thousand eight hundred
- Ordinal
- 21800th
- Binary
- 101010100101000
- Octal
- 52450
- Hexadecimal
- 0x5528
- Base64
- VSg=
- One's complement
- 43,735 (16-bit)
- Scientific notation
- 2.18 × 10⁴
- As a duration
- 21,800 s = 6 hours, 3 minutes, 20 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒁹𒁹𒁹𒁹𒁹𒁹 𒁹𒁹𒁹 𒌋𒌋
- Egyptian hieroglyphic
- 𓂍𓂍𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢
- Greek (Milesian)
- ͵καωʹ
- Mayan (base 20)
- 𝋢·𝋮·𝋪·𝋠
- Chinese
- 二萬一千八百
- Chinese (financial)
- 貳萬壹仟捌佰
Digit at this position in famous constants
- π — Pi (π)
- Digit 21,800 = 0
- e — Euler's number (e)
- Digit 21,800 = 0
- φ — Golden ratio (φ)
- Digit 21,800 = 4
- √2 — Pythagoras's (√2)
- Digit 21,800 = 9
- ln 2 — Natural log of 2
- Digit 21,800 = 3
- γ — Euler-Mascheroni (γ)
- Digit 21,800 = 6
Also seen as
Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 21800, here are decompositions:
- 13 + 21787 = 21800
- 43 + 21757 = 21800
- 61 + 21739 = 21800
- 73 + 21727 = 21800
- 127 + 21673 = 21800
- 139 + 21661 = 21800
- 151 + 21649 = 21800
- 199 + 21601 = 21800
Showing the first eight; more decompositions exist.
UTF-8 encoding: E5 94 A8 (3 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.85.40.
- Address
- 0.0.85.40
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.85.40
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The digit sequence 21800 first appears in π at position 43,885 of the decimal expansion (the 43,885ordinal-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.
Related reading
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros.