Properties of the Number 20809

Twenty Thousand Eight Hundred Nine

Basics

Value: 20808 → 20809 → 20810

Parity: odd

Prime: Yes

Previous Prime: 20807

Next Prime: 20849

Digit Sum: 19

Digital Root: 1

Palindrome: No

Factorization: 20809

Divisors: 1, 20809

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000101001001

Octal: 50511

Duodecimal: 10061

Hexadecimal: 5149

Square: 433014481

Square Root: 144.25324953012324

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: No

Perfect Number: No

Special

Kaprekar Constant: No

Munchausen Constant: No

Armstrong Number: No

Kaprekar Number: No

Catalan Number: No

Vampire Number: No

Taxicab Number: No

Super Prime: No

Friedman Number: No

Fermat Number: No

Cullen Number: No

OEIS Sequences

Primes of the form 2·n²+1. A90698

a(n) is the smallest prime q such that (r-q)/(q-p) = n, where p<q<r are consecutive primes (or 0 if no such prime exists). A179210

Primes p such that q-p = 40, where q is the next prime after p. A126721

Primes p such that A001175(p) = (p-1)/6. A308791

Noncomposite numbers in the western ray of the Ulam spiral as oriented on the March 1964 cover of Scientific American. A168025

Primes of the form m·rad(m)+1, where rad = A007947 (squarefree kernel). A78324

a(n) = ∑_{k=0..floor(2·n/9)} binomial(2·n-6·k,3·k). A392405

Primes p such that (r-p)/log(p) > 4, where r is the next prime after p. A82889

a(n) = 18·n² + 1. A157889

Lower ends of record gaps between numbers that are either prime or twice a prime. A290488