Properties of the Number 20909

Twenty Thousand Nine Hundred Nine

Basics

Value: 20908 → 20909 → 20910

Parity: odd

Prime: No

Previous Prime: 20903

Next Prime: 20921

Digit Sum: 20

Digital Root: 2

Palindrome: No

Factorization: 7 × 29 × 103

Divisors: 1, 7, 29, 103, 203, 721, 2987, 20909

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000110101101

Octal: 50655

Duodecimal: 10125

Hexadecimal: 51ad

Square: 437186281

Square Root: 144.59944674859582

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) = Smallest nontrivial number k > 9 such that |first (leftmost) decimal digit of k - second digit + third digit - fourth digit ...| = n. A60982

Smallest number m such that first digit - second digit + third digit - fourth digit ... (of m) = n. A61479

a(n) = Smallest nontrivial number k > 9 such that first (leftmost) digit - second digit + third digit - fourth digit ... of k = n. A61882

Numbers k such that 3·2^k + 1 is prime. A2253

Positive integers k such that (k+1)⁴ has a divisor congruent to -1 modulo k. A350916

Minimum number k for which the digital sum of k·n is 2·n. A147822

Numbers k such that 3·2^k + 1 is a prime factor of a generalized Fermat number 5^{2^m} + 1 for some m. A268658

Numbers n such that 3·2ⁿ + 1 is a prime factor of a generalized Fermat number 12^{2^m} + 1 for some m. A268660

a(0) = 9, a(1) = 9, and a(n) = 3·a(n-1) - a(n-2) - 4 for n >= 2. A350919

Composite numbers k coprime to 8 such that k divides Pell(k - Kronecker(8,k)), Pell = A000129. A327651