Properties of the Number 20810

Twenty Thousand Eight Hundred Ten

Basics

Value: 20809 → 20810 → 20811

Parity: even

Prime: No

Previous Prime: 20809

Next Prime: 20849

Digit Sum: 11

Digital Root: 2

Palindrome: No

Factorization: 2 × 5 × 2081

Divisors: 1, 2, 5, 10, 2081, 4162, 10405, 20810

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000101001010

Octal: 50512

Duodecimal: 10062

Hexadecimal: 514a

Square: 433056100

Square Root: 144.25671561490648

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

a(n) = prime(n+1)² + prime(n)². A69484

Triangle T(n,k) read by rows: T(n,k) = the number of ways of seating n people around a table for the second time so that k pairs are maintained. Reflected and rotated sequences are counted as one. A326411

O.g.f.: exp( ∑_n>=1 -(σ(2·n²) - σ(n²)) * (-x)ⁿ/n ). A215603

G.f.: A(x) = exp( ∑_n>=1 σ(n)*A000204(n)*xⁿ/n ). A156234

Number of integer partitions of prime(n) into a prime number of prime parts. A316154

T(n,k)=Number of idempotent n X n 0..k matrices of rank n-2. A224118

a(0) = 1, a(n) = 18·n² + 2 for n>0. A10008

Length of hypotenuse squared in right triangle formed by a prime spiral plotted in Cartesian coordinates. A48851

Hypotenuses of special Pythagorean triples constructed from twin primes as follows: {u, w}={p,p+2}; side a=2p(p+2), side b=(p+2)²-p² and the terms of sequence are values of c=a(n)=p²+(p+2)²=φ(a/2)+1+σ(a/2)+1. A63533

a(n) is twice the coefficient of 1 in the fundamental unit of Q(sqrt(A000037(n))) where A000037 lists the nonsquare numbers (Version 2). A346419