Properties of the Number 20840

Twenty Thousand Eight Hundred Forty

Basics

Value: 20839 → 20840 → 20841

Parity: even

Prime: No

Previous Prime: 20809

Next Prime: 20849

Digit Sum: 14

Digital Root: 5

Palindrome: No

Factorization: 2 ³ × 5 × 521

Divisors: 1, 2, 4, 5, 8, 10, 20, 40, 521, 1042

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000101101000

Octal: 50550

Duodecimal: 10088

Hexadecimal: 5168

Square: 434305600

Square Root: 144.3606594609487

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 length n+3 0..k arrays with no pair in any consecutive four terms totalling exactly k. A246479

T(n,k)=Number of nXnXn triangular 0..k arrays with no element lying outside the (possibly reversed) range delimited by its sw and se neighbors. A214352

a(n) is the smallest number which can be represented as the sum of n distinct nonzero squares in exactly n ways, or 0 if no such number exists. A350241

Maximal number of 1432 patterns in a permutation of 1,2,...,n. A100354

a(n) = p(n)*p(n+2)-p(n+1), where p(n) is the n-th prime. A152530

Relative of Hofstadter Q-sequence: a(n) = max(0, n+20830) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0. A283887

Number of compositions of n such that the cardinality of the set of parts is 2. A131661

Triangle read by rows: T(n,k) is the number of non-isomorphic multiset partitions of weight n with k parts and no singletons or vertices that appear only once, 0 <= k <= floor(n/2). A369287

G.f.: A(x) = ∏_n>=1 [ (1-x)⁵*(1 + 5x + 15x² +...+ n(n+1)(n+2)(n+3)/4!*x^n-1) ]. A129358

Triangle read by rows: T(n,k) = A(k,n-k), 1 <= k < n, 2 <= n, where A(m,n) is the number of distinct strings consisting of one X, 2·m-1 Y's and 2·n-1 Z's in which the X lies to the right of at least m Y's and at least n Z's. A351583