Properties of the Number 81809

Eighty-One Thousand Eight Hundred Nine

Basics

Value: 81808 → 81809 → 81810

Parity: odd

Prime: No

Previous Prime: 81799

Next Prime: 81817

Digit Sum: 26

Digital Root: 8

Palindrome: No

Factorization: 7 × 13 × 29 × 31

Divisors: 1, 7, 13, 29, 31, 91, 203, 217, 377, 403

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 10011111110010001

Octal: 237621

Duodecimal: 3B415

Hexadecimal: 13f91

Square: 6692712481

Square Root: 286.0227263697764

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 nXk 0..1 arrays with every element unequal to 0, 1, 2, 3, 4, 7 or 8 king-move adjacent elements, with upper left element zero. A317118

Numbers k such that σ(k)/φ(k) = 16/9. A164647

a(n) = 169·n² + 13. A158548

Expansion of x²*(10-5·x+x²)/((1-x)⁴*(1-x²)). A331429

Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 44. A31722

Numbers such that the sum of the squares of the largest and the smallest prime divisor equals the sum of the squares of the other distinct prime divisors. A199857

Number of nX3 0..1 arrays with every element unequal to 0, 1, 2, 3, 4, 7 or 8 king-move adjacent elements, with upper left element zero. A317113

Number of nX7 0..1 arrays with every element unequal to 0, 1, 2, 3, 4, 7 or 8 king-move adjacent elements, with upper left element zero. A317117

Numbers k that divide the k-th little Schroeder number. A372903

a(n) is the smallest number m such that φ(m)+σ(m)=n*π(m). A145747