Properties of the Number 21828

Twenty-One Thousand Eight Hundred Twenty-Eight

Basics

Value: 21827 → 21828 → 21829

Parity: even

Prime: No

Previous Prime: 21821

Next Prime: 21839

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 2 ² × 3 × 17 × 107

Divisors: 1, 2, 3, 4, 6, 12, 17, 34, 51, 68

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101010101000100

Octal: 52504

Duodecimal: 10770

Hexadecimal: 5544

Square: 476461584

Square Root: 147.7430201397007

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

Numbers m with C(2·m, m) + prime(m) prime, where C(2·m, m) = (2·m)!/(m!)². A236242

The dimension of the space of invariant tensors in the n-th tensor power of the adjoint representation of the exceptional Lie algebra E7. A179683

Solution of the complementary equation a(n) = 2·a(n-1) - a(n-2) + b(n-1) + n, where a(0) = 1, a(1) = 2, b(0) = 3, and (a(n)) and (b(n)) are increasing complementary sequences. A294872

Numbers k such that k and k+1 are both hoax numbers (A019506). A329935

Expansion of e.g.f. exp( ∑_k>=0 x^3·k+4 / (3·k+4)! ). A365894

Numbers k such that 7·10^k - 23 is prime. A272271

G.f. = φ³*F³, where φ = g.f. for A028930, F = g.f. for A028959. A328534

Operation count to create all permutations of n distinct elements using the "streamlined" version of Algorithm L (lexicographic permutation generation) from Knuth's The Art of Computer Programming, Vol. 4, chapter 7.2.1.2. Sequence gives number of comparisons required to find j in step L2.2'. A79750

Number of n X 4 0..4 arrays with each element·equal to the number its horizontal and vertical neighbors equal to 3,0,2,4,1 for x=0,1,2,3,4. A196452

Decimal expansion of 1/824. A21828