Properties of the Number 18921

Eighteen Thousand Nine Hundred Twenty-One

Basics

Value: 18920 → 18921 → 18922

Parity: odd

Prime: No

Previous Prime: 18919

Next Prime: 18947

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 3 × 7 × 17 × 53

Divisors: 1, 3, 7, 17, 21, 51, 53, 119, 159, 357

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 100100111101001

Octal: 44751

Duodecimal: AB49

Hexadecimal: 49e9

Square: 358004241

Square Root: 137.55362590640786

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

Centered 20-gonal (or icosagonal) numbers. A69133

25-gonal pyramidal numbers: a(n) = n*(n+1)*(23·n-20)/6. A256645

Decimal representation of the x-axis, from the left edge to the origin, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 403", based on the 5-celled von Neumann neighborhood. A281846

a(n) = (3·n - 1)*(4·n - 1). A33578

a(n) is the smallest multiple of n such that a(n) mod 100 = n and S(n)=n where S(n) is the sum of the base-ten digits of n, or 0 if no such a(n) exists. A75154

Numbers n such that there are integers a < b with a²+(a+1)²+...+(n-1)² = (n+1)²+(n+2)²+...+b². A94552

Numbers k such that 6·p(k)*p(k+1)*p(k+2)*p(k+3)*p(k+4)-1 and 6·p(k)*p(k+1)*p(k+2)*p(k+3)*p(k+4)+1 are twin primes with p(h) = h-th prime. A129310

a(n) = (n³ + 18·n² + 17·n + 6)/6. A143058

Let S denote the palindromes in the language {0,1,2,...,n-1}*; a(n) = number of words of length 4 in the language SS. A187277

Solution (a(n)) of the complementary equation a(n) = 2·a(n-1) - a(n-2) + b(n-2); see Comments. A305329