Properties of the Number -1781

Seven Hundred Eighty-One

Basics

Value: -1782 → -1781 → -1780

Parity: odd

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 17

Digital Root: 8

Palindrome: No

Factorization: 13 × 137

Divisors: 1, 13, 137, 1781

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: -11011110101

Octal: -3365

Duodecimal: -1045

Hexadecimal: -6f5

Square: 3171961

Square Root: 42.20189569201838

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

G.f.: ∑_n=-oo..+oo x^n*(n+1/2) * C(x)^3·n-3, where C(x) = 1 + x·C(x)² is the g.f. of the Catalan numbers (A000108). A355348

Expansion of (1-x)^-1/(1-2·x+2·x²+2·x³). A77862

A nonsense sequence. A152462

Numbers that are the sum of 10 positive 6th powers. A3366

Ordered hypotenuses of primitive Pythagorean triangles having legs that add up to a square. A88319

Frobenius number of the subsemigroup of the natural numbers generated by successive pairs of Fibonacci numbers. A59769

Numbers whose smallest prime factor is 13. A84970

Triangle read by rows: T(n, k) = number of hill-free Dyck paths (i.e., no peaks at height 1) of semilength n and having k peaks. A100754

Numbers k such that the first k digits of e form a prime. A64118

T(n,k) is the number of n-bead necklaces labeled with numbers -k..k allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2. A209485