20,981
20,981 is a prime, odd.
20,981 (twenty thousand nine 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, 0x51F5.
Interestingness
Properties
- Parity
- Odd
- Digit count
- 5
- Digit sum
- 20
- Digit product
- 0
- Digital root
- 2
- Palindrome
- No
- Bit width
- 15 bits
- Reversed
- 18,902
- Recamán's sequence
- a(41,877) = 20,981
- Square (n²)
- 440,202,361
- Cube (n³)
- 9,235,885,736,141
- Divisor count
- 2
- σ(n) — sum of divisors
- 20,982
- φ(n) — Euler's totient
- 20,980
Primality
20,981 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√20,981 = [144; (1, 5, 1, 1, 2, 2, 1, 3, 1, 3, 41, 8, 3, 1, 21, 1, 1, 8, 1, 5, 57, 1, 3, 2, …)]
Representations
- In words
- twenty thousand nine hundred eighty-one
- Ordinal
- 20981st
- Binary
- 101000111110101
- Octal
- 50765
- Hexadecimal
- 0x51F5
- Base64
- UfU=
- One's complement
- 44,554 (16-bit)
- Scientific notation
- 2.0981 × 10⁴
- As a duration
- 20,981 s = 5 hours, 49 minutes, 41 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓂍𓂍𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵κϡπαʹ
- Mayan (base 20)
- 𝋢·𝋬·𝋩·𝋡
- Chinese
- 二萬零九百八十一
- Chinese (financial)
- 貳萬零玖佰捌拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 20,981 = 5
- e — Euler's number (e)
- Digit 20,981 = 3
- φ — Golden ratio (φ)
- Digit 20,981 = 0
- √2 — Pythagoras's (√2)
- Digit 20,981 = 6
- ln 2 — Natural log of 2
- Digit 20,981 = 2
- γ — Euler-Mascheroni (γ)
- Digit 20,981 = 8
Also seen as
UTF-8 encoding: E5 87 B5 (3 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.81.245.
- Address
- 0.0.81.245
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.81.245
Unspecified address (0.0.0.0/8) — "this network" placeholder.
The digit sequence 20981 first appears in π at position 86,928 of the decimal expansion (the 86,928ordinal-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
- Prime numbers — The building blocks of arithmetic: what primes are, why they matter, and how we find them.
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros.