Properties of the Number 8181

Eight Thousand One Hundred Eighty-One

Basics

Value: 8180 → 8181 → 8182

Parity: odd

Prime: No

Previous Prime: 8179

Next Prime: 8191

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 3 ⁴ × 101

Divisors: 1, 3, 9, 27, 81, 101, 303, 909, 2727, 8181

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

8509 Try Today's Challenge

Representations

Binary: 1111111110101

Octal: 17765

Duodecimal: 4899

Hexadecimal: 1ff5

Square: 66928761

Square Root: 90.44888059008801

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

Number of disconnected 2-regular graphs on n vertices. A165652

Numbers missing from A102370. A102371

Numbers k for which the digital sum of k contains the same distinct digits as k itself. A249515

Number of ways to tile an n X 1 strip with 1 X 1 squares and 2 X 1 dominoes with the restriction that no three consecutive tiles are of the same type. A137200

Numbers m such that A338038(m) = A338038(A004086(m)) where A004086(i) is i read backwards and A338038(i) is the sum of the primes and exponents in the prime factorization of i ignoring 1-exponents; palindromes and multiples of 10 are excluded. A338039

Triangle read by rows: T(n,k) is the number of deco polyominoes of height n and vertical height (i.e., number of rows) k (1 <= k <= n). A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column. A121692

a(n) = 2ⁿ⁺¹ - n + 1. A132753

Numbers consisting of ones and eights. A213084

Decimal representation of the x-axis, from the left edge to the origin, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 49", based on the 5-celled von Neumann neighborhood. A278468

Numbers k for which A003958(σ(k)) = 2·A003958(k), where A003958 is multiplicative with a(p^e) = (p-1)^e and σ is the sum of divisors function. A351447