Properties of the Number 21309

Twenty-One Thousand Three Hundred Nine

Basics

Value: 21308 → 21309 → 21310

Parity: odd

Prime: No

Previous Prime: 21283

Next Prime: 21313

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 3 × 7103

Divisors: 1, 3, 7103, 21309

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101001100111101

Octal: 51475

Duodecimal: 103B9

Hexadecimal: 533d

Square: 454073481

Square Root: 145.9760254288354

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

Sums of successive Motzkin numbers. A5554

Expansion of g.f.: 1/((1 - 2·x² + x⁴ + 2·x⁶ - x⁸)*(1 - 2·x² - x⁴ + 2·x⁶ - x⁸)). A147607

Magic sums of 3 X 3 magic squares composed of primes in an arithmetic progression. A269324

Odd numbers k such that φ(k) and cototient(k) have the same prime signature. A280927

n/3 analog of Keith numbers. A282767

Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 78 ones. A31846

Numbers k such that usigma(uphi(k)) = uphi(usigma(k)), where usigma is the sum of unitary divisors function (A034448) and uphi is the unitary totient function (A047994). A329730

Coefficient of xⁿ in the expansion of ( (1+x)³ + x³ )ⁿ. A370287

E.g.f.: ∑_n>=0 xⁿ * exp( 2·x*exp(n·x) ) / n!. A340913

Number of ballot sequences of length n with exactly 8 fixed points. A239119