Properties of the Number 21819

Twenty-One Thousand Eight Hundred Nineteen

Basics

Value: 21818 → 21819 → 21820

Parity: odd

Prime: No

Previous Prime: 21817

Next Prime: 21821

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 3 × 7 × 1039

Divisors: 1, 3, 7, 21, 1039, 3117, 7273, 21819

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010100111011

Octal: 52473

Duodecimal: 10763

Hexadecimal: 553b

Square: 476068761

Square Root: 147.7125587077822

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

T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and diagonal sum equal to 2 3 4 6 or 7 and every 3X3 column and antidiagonal sum not equal to 2 3 4 6 or 7. A252407

A partition product of Stirling₁ type [parameter k = 3] with biggest-part statistic (triangle read by rows). A157393

A partition product of Stirling₁ type [parameter k = -3] with biggest-part statistic (triangle read by rows). A157383

A partition product of Stirling₂ type [parameter k = -3] with biggest-part statistic (triangle read by rows). A157399

A partition product of Stirling₂ type [parameter k = 3] with biggest-part statistic (triangle read by rows). A157403

T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 2, 3, 4 or 5 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. A300923

Triangle read by rows: T(n,k) is the number of subpermutations of an n-set, whose orbits are each of size at most k with at least one orbit of size exactly k, and without fixed points. Equivalently, T(n,k) is the number of partial derangements of an n-set each of whose orbits is of size at most k with at least one orbit of size exactly k, and without fixed points. A261765

Irregular table whose rows list the nontrivial cycles of the ghost iteration A329201, starting with the smallest member. A329342

a(n)/2^n-1 is the expected win if one of two baskets is chosen randomly and the player optimally chooses the coins with values from 1 to n (see Comments for details). A391791

Number of compositions of n with exactly 1 adjacent equal pair of parts. A106357