Properties of the Number -1681

Six Hundred Eighty-One

Basics

Value: -1682 → -1681 → -1680

Parity: odd

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 16

Digital Root: 7

Palindrome: No

Factorization: 41 ²

Divisors: 1, 41, 1681

Polygonal

Triangular: No

Square: Yes

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

5184 Try Today's Challenge

Representations

Binary: -11010010001

Octal: -3221

Duodecimal: -B81

Hexadecimal: -691

Square: 2825761

Square Root: 41

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

Dirichlet g.f.: 1 / ζ(s-2). A334657

a(1) = 1, a(2) = -5; a(n) = -n² * ∑_{d∣n, d < n} a(d) / d². A359485

a(1) = 1, a(2) = 3; a(n) = n² * ∑_{d∣n, d < n} (-1)^n/d a(d) / d². A361986

Numerators of the second differences of the sequence of fractions (-1)ⁿ⁺¹*A176618(n)/A172031(n). A195240

Expansion of (1-x)^-1/(1+2·x-x²). A77921

Expansion of 1/(1+x+x²+2·x³). A77976

a(1) = 1; a(n) = n² * ∑_{d∣n, d < n} (-1)^n/d a(d) / d². A361987

Numerator of Euler(n, 1/6). A156187

First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 483", based on the 5-celled von Neumann neighborhood. A272346

Numerator of [xⁿ] in the Taylor series arccosh(exp(x)-arctanh(x))= x-x²/6-x³/72 -359·x⁴/2160 -1681·x⁵/51840 -52981·x⁶/435456 -... A13325