Properties of the Number 81810

Eighty-One Thousand Eight Hundred Ten

Basics

Value: 81809 → 81810 → 81811

Parity: even

Prime: No

Previous Prime: 81799

Next Prime: 81817

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 2 × 3 ⁴ × 5 × 101

Divisors: 1, 2, 3, 5, 6, 9, 10, 15, 18, 27

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 10011111110010010

Octal: 237622

Duodecimal: 3B416

Hexadecimal: 13f92

Square: 6692876100

Square Root: 286.02447447727263

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

Let i be in {1,2,3,4} and let r >= 0 be an integer. Let p = {p₁, p₂, p₃, p₄} = {-2,0,1,2}, n=3·r+p_i, and define a(-2)=0. Then a(n)=a(3·r+p_i) gives the quantity of H_9,2,0 tiles in a subdivided H_9,i,r tile after linear scaling by the factor Q^r, where Q=sqrt(x²-1) with x=2·cos(π/9). A187500

Triangular numbers n such that each decimal digit of n is equal to the difference of at least two other digits of n. A255917

Call n/m a superdivisor of n if n/m + n divides (n/m)^n/m + n, (n/m)ⁿ + n/m and n^n/m + n/m. This sequence gives the smallest number with n superdivisors. A272538

Non-palindromic numbers such that either x=q1.Rev[x] or Rev[x]=q2.x, where R[x]=A004086[x] and q1 or q2 are integers not divisible by 10. A71687

Triangular numbers composed of digits {0,1,8}. A119045

a(n) is the largest number in row n of A380920. A380967

Triangular numbers whose sum of prime factors (with repetition) is also triangular. A76169

Triangular numbers for which the sum of the digits equals the sum of the digits of the next triangular number. A117511

Triangular numbers which are sums of 6 consecutive primes. A173423

Multiplicity of highest weight (or singular) vectors associated with character chi₆₆ of Monster module. A34454