Properties of the Number 81405

Eighty-One Thousand Four Hundred Five

Basics

Value: 81404 → 81405 → 81406

Parity: odd

Prime: No

Previous Prime: 81401

Next Prime: 81409

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 3 ⁵ × 5 × 67

Divisors: 1, 3, 5, 9, 15, 27, 45, 67, 81, 135

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 10011110111111101

Octal: 236775

Duodecimal: 3B139

Hexadecimal: 13dfd

Square: 6626774025

Square Root: 285.31561471465244

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

Triangle read by rows, 3^k*S₃(n, k) where S_m(n, k) are the Stirling-Frobenius subset numbers of order m; n >= 0, k >= 0. A225466

Sums of 5 distinct powers of 5. A38477

G.f.: A(x) = ( ∑_n>=0 9ⁿ*(2·n+1) * (-x)^n*(n+1/2) )^-1/3. A202438

Number of times the n-th prime appears among the decimal digits of 2^2ⁿ + 1, the Fermat numbers. A78671

a(n) = (n+1)*a(n-2) with a(0) = a(1) = 1. A81405