Properties of the Number 20921

Twenty Thousand Nine Hundred Twenty-One

Basics

Value: 20920 → 20921 → 20922

Parity: odd

Prime: Yes

Previous Prime: 20903

Next Prime: 20929

Digit Sum: 14

Digital Root: 5

Palindrome: No

Factorization: 20921

Divisors: 1, 20921

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 101000110111001

Octal: 50671

Duodecimal: 10135

Hexadecimal: 51b9

Square: 437688241

Square Root: 144.64093473149293

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

Odd primes generated recursively: a(1) = 3, a(n) = Min {p is prime; p divides Q+2}, where Q is the product of previous terms in the sequence. A125045

Primes p for which the period of reciprocal = (p-1)/8. A56213

Prime number spiral (clockwise, Southwest spoke). A54568

Number of odious primes (A027697) in range ]2ⁿ,2ⁿ⁺¹]. A95005

Hyperartiads. A270798

Fourth prime p such that (p+n)²+n is prime but (p+j)²+j is not prime for all 0<j<n. A238676

Primes whose position in the Wythoff array is immediately followed by a prime both in the next column and the next row. A352537

Numbers k such that the continued fraction for sqrt(k) has period 87. A20426

a(1) = 1, a(n) = prime equal to n-th partial sum of A073852. A73854

Let p(k) = k-th prime; sequence gives primes q of the form q = k·p(k) - 1 for some k. A96065