Properties of the Number -781

Seven Hundred Eighty-One

Basics

Value: -782 → -781 → -780

Parity: odd

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 16

Digital Root: 7

Palindrome: No

Factorization: 11 × 71

Divisors: 1, 11, 71, 781

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: -1100001101

Octal: -1415

Duodecimal: -551

Hexadecimal: -30d

Square: 609961

Square Root: 27.94637722496424

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

Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of ∏_j>=1 (1 - j^k*x^j). A292166

Triangle c(n,k) of the numerators of coefficients [x^k] P(n,x) of the polynomials P(n,x) of A129891. A140749

G.f.: ∑_n>=0 (xⁿ - 1)ⁿ * xⁿ / (1-x)ⁿ⁺¹. A243919

First differences of A060819(n-4)*A060819(n). A185688

Alternating sum of 9-gonal (or nonagonal) numbers. A266086

a(n) = 2³ⁿ⁺¹*cos(nB), where B is the angle opposite side CA in a triangle ABC having sidelengths |BC|=2, |CA| = 3, |AB| = 4; ABC is the smallest integer-sided scalene triangle. A375881

Expansion of log(1+tan(x))/cos(x). A9372

Central polygonal numbers (the Lazy Caterer's sequence): n(n+1)/2 + 1; or, maximal number of pieces formed when slicing a pancake with n cuts. A124

Number of regions in regular n-gon with all diagonals drawn. A7678

a(n) = (5ⁿ - 1)/4. A3463