Properties of the Number 81840

Eighty-One Thousand Eight Hundred Forty

Basics

Value: 81839 → 81840 → 81841

Parity: even

Prime: No

Previous Prime: 81839

Next Prime: 81847

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 2 ⁴ × 3 × 5 × 11 × 31

Divisors: 1, 2, 3, 4, 5, 6, 8, 10, 11, 12

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2730 Try Today's Challenge

Representations

Binary: 10011111110110000

Octal: 237660

Duodecimal: 3B440

Hexadecimal: 13fb0

Square: 6697785600

Square Root: 286.07691273501956

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

a(n) = 2·binomial(n,4). A34827

a(n) = binomial(2·n, n) mod ((n+1)*(n+2)*(n+3)*(n+4)). A65346

Numbers with prime factorization p·q*r·s*t⁴ (where p, q, r, s, t are distinct primes). A190110

Number of non-equivalent ways to tile an n X n X n triangular area with two 2 X 2 X 2 triangular tiles and an appropriate number (= n²-8) of 1 X 1 X 1 tiles. A286444

a(n) = A351477(n) * FA where F is the Fermat point of a primitive integer-sided triangle ABC with A < B < C < 2*π/3 and FA + FB + FC = A336329(n). A351801

a(n) = 169·n² + 2·n. A158220

Number of Sidon subsets of {1,...,n} of size 4. A241688

a(n) = n*(n + 1)*(16·n - 1)/6. A304659

Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 13. A31691

Number of reduced words of length n in Coxeter group on 5 generators S_i with relations (S_i)² = (S_i S_j)⁷ = I. A164354