Properties of the Number 19805

Nineteen Thousand Eight Hundred Five

Basics

Value: 19804 → 19805 → 19806

Parity: odd

Prime: No

Previous Prime: 19801

Next Prime: 19813

Digit Sum: 23

Digital Root: 5

Palindrome: No

Factorization: 5 × 17 × 233

Divisors: 1, 5, 17, 85, 233, 1165, 3961, 19805

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 100110101011101

Octal: 46535

Duodecimal: B565

Hexadecimal: 4d5d

Square: 392238025

Square Root: 140.73023839957068

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 defective 4-colorings of an n X k 0..3 array connected horizontally, antidiagonally and vertically with exactly two mistakes, and colors introduced in row-major 0..3 order. A229672

Number of partitions of n into at most 8 parts. A8637

Let p(n) be the n-th prime congruent to 1 mod 4. Then a(n) = the least k for which m²+1=p(n)*k² has a solution. A94049

G.f.: ∑_n>=0 (1 - (1-x)ⁿ)ⁿ. A220353

Determinant of the (p_n-1)/2 X (p_n-1)/2 matrix with (i,j)-entry being the Legendre symbol ((j-i)/p_n), where p_n is the n-th prime. A228077

Numbers of the form p·q*r where p, q, r are distinct primes congruent to 1 mod 4 such that Legendre(p/q) = Legendre(p/r) = Legendre(q/r) = -1. A323271

Regular triangle read by rows where T(n, k) is the number of set partitions of {1, ..., n} with no block containing k cyclically successive vertices, n >= 1, 2 <= k <= n + 1. A323955

Denominators of continued fraction convergents to sqrt(317). A41599

Smallest integer y satisfying the Pell equation x² - n·y² = -1 for the values of n given in A031396. A130227

Number of defective 4-colorings of an nX3 0..3 array connected horizontally, antidiagonally and vertically with exactly two mistakes, and colors introduced in row-major 0..3 order. A229667