12,821
12,821 is a prime, odd.
12,821 (twelve thousand eight hundred twenty-one) is an odd 5-digit number. It is a prime number — divisible only by 1 and itself. Its digits read the same forwards and backwards, so it is a palindromic number. Written other ways, in hexadecimal, 0x3215.
Interestingness
Properties
- Parity
- Odd
- Digit count
- 5
- Digit sum
- 14
- Digit product
- 32
- Digital root
- 5
- Palindrome
- Yes
- Bit width
- 14 bits
- Recamán's sequence
- a(48,633) = 12,821
- Square (n²)
- 164,378,041
- Cube (n³)
- 2,107,490,863,661
- Divisor count
- 2
- σ(n) — sum of divisors
- 12,822
- φ(n) — Euler's totient
- 12,820
Primality
12,821 is prime. It has exactly two divisors: 1 and itself.
Divisors & multiples
Sums & aliquot sequence
Continued fraction of √n
√12,821 = [113; (4, 2, 1, 5, 1, 3, 1, 1, 56, 17, 2, 2, 17, 56, 1, 1, 3, 1, 5, 1, 2, 4, 226)]
Period length 23 — the block in parentheses repeats forever.
Representations
- In words
- twelve thousand eight hundred twenty-one
- Ordinal
- 12821st
- Binary
- 11001000010101
- Octal
- 31025
- Hexadecimal
- 0x3215
- Base64
- MhU=
- One's complement
- 52,714 (16-bit)
- Scientific notation
- 1.2821 × 10⁴
- As a duration
- 12,821 s = 3 hours, 33 minutes, 41 seconds
As an angle
Historical numeral systems
- Babylonian (base 60)
- 𒁹𒁹𒁹 𒌋𒌋𒌋𒁹𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓂍𓆼𓆼𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓏺
- Greek (Milesian)
- ͵ιβωκαʹ
- Mayan (base 20)
- 𝋡·𝋬·𝋡·𝋡
- Chinese
- 一萬二千八百二十一
- Chinese (financial)
- 壹萬貳仟捌佰貳拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 12,821 = 2
- e — Euler's number (e)
- Digit 12,821 = 0
- φ — Golden ratio (φ)
- Digit 12,821 = 9
- √2 — Pythagoras's (√2)
- Digit 12,821 = 4
- ln 2 — Natural log of 2
- Digit 12,821 = 1
- γ — Euler-Mascheroni (γ)
- Digit 12,821 = 0
Also seen as
UTF-8 encoding: E3 88 95 (3 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.50.21.
- Address
- 0.0.50.21
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.50.21
Unspecified address (0.0.0.0/8) — "this network" placeholder.
Heard as a frequency, 12,821 Hz is closest to:
- Concert pitch (A4 = 440 Hz): G9 (12543.9 Hz, +38¢)
- Scientific pitch (C4 = 256 Hz): G♯9 (13004 Hz, -25¢)
- Baroque pitch (A4 = 415 Hz): G♯9 (12534.7 Hz, +39¢)
The digit sequence 12821 first appears in π at position 97,930 of the decimal expansion (the 97,930ordinal-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.