Properties of the Number 20827

Twenty Thousand Eight Hundred Twenty-Seven

Basics

Value: 20826 → 20827 → 20828

Parity: odd

Prime: No

Previous Prime: 20809

Next Prime: 20849

Digit Sum: 19

Digital Root: 1

Palindrome: No

Factorization: 59 × 353

Divisors: 1, 59, 353, 20827

Polygonal

Triangular: No

Square: No

Pentagonal: Yes

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000101011011

Octal: 50533

Duodecimal: 10077

Hexadecimal: 515b

Square: 433763929

Square Root: 144.31562631953616

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

Semiprimes of the form n*(3·n-1)/2. A245365

Number of plane regions after drawing (in general position) a convex n-gon and all its diagonals. A27927

Pentagonal numbers (A000326) which are the sum of 2 other positive pentagonal numbers. A136117

Numbers n such that Fibonacci(n) is not squarefree, but for all proper divisors k of n, Fibonacci(k) is squarefree. A65069

A (-1,1) Somos-4 sequence associated with the elliptic curve y² + y = x³ + x. A178384

a(n) = n·prime(prime(n)) - prime(n)². A230098

G.f.: ∑_n>=0 xⁿ * (1+x)^σ(n). A227236

Number of set partitions of [n] such that j is member of block b only if b = 1 or at least one of j-1, ..., j-4 is member of a block >= b-1. A287667

a(0) = 1, a(n) = 17·n² + 2 for n>0. A10007

Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=2, r=3, I={-1}. A80011