Properties of the Number -1981

Nine Hundred Eighty-One

Basics

Value: -1982 → -1981 → -1980

Parity: odd

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 19

Digital Root: 1

Palindrome: No

Factorization: 7 × 283

Divisors: 1, 7, 283, 1981

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: -11110111101

Octal: -3675

Duodecimal: -1191

Hexadecimal: -7bd

Square: 3924361

Square Root: 44.50842616853577

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

Numerator of Bernoulli(n, -1/5). A157871

Coefficient array of orthogonal polynomials P(n,x)=(x-n)*P(n-1,x)-(n-1)²*P(n-2,x), P(0,x)=1, P(1,x)=x-1. A182823

First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 205", based on the 5-celled von Neumann neighborhood. A270732

First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 435", based on the 5-celled von Neumann neighborhood. A272152

Triangle T(n,k), read by rows, given by T(n,0)=1, T(n,1)=2ⁿ⁺¹-n-2, T(n,n)=(-1)^n-1 for n > 0, T(n,k)=T(n-1,k)-T(n-1,k-1) for 1 < k < n. A232774

Central polygonal numbers: a(n) = n² - n + 1. A2061

a(n) is the smallest m > 1 such that m divides ∑_k=1..m prime(k)ⁿ. A85450

G.f.: ∏_k>=1 (1 + x^{2·k - 1}) / (1 - x^2·k). A6950

a(n) = 4·n² - 6·n + 3. A54569

Triangle read by rows of partial sums of binomial coefficients: T(n,k) = ∑_i=0..k binomial(n,i) (0 <= k <= n); also dimensions of Reed-Muller codes. A8949