Properties of the Number -1820

Eight Hundred Twenty

Basics

Value: -1821 → -1820 → -1819

Parity: even

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 11

Digital Root: 2

Palindrome: No

Factorization: 2 ² × 5 × 7 × 13

Divisors: 1, 2, 4, 5, 7, 10, 13, 14, 20, 26

Polygonal

Triangular: No

Square: No

Pentagonal: Yes

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: -11100011100

Octal: -3434

Duodecimal: -1078

Hexadecimal: -71c

Square: 3312400

Square Root: 42.661458015403085

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

T(j,k) are the numerators s in the representation R = s/t + (2/π)*u/v of the resistance between two nodes separated by the distance vector (j,k) in an infinite square lattice of one-ohm resistors, where T(j,k), j >= 0, 0 <= k <= j, is a triangle read by rows. A355565

Expansion of Product (1 - x^k)¹⁰ in powers of x. A10818

Coefficient array for certain polynomials N(4; k,x) (rising powers in x). A62751

Expansion of q*ψ(q⁹)/ψ(q) in powers of q. A124243

Expansion of (1/3) * (c(q²)² / c(q)) / (b(q²)² / b(q)) in powers of q where b(), c() are cubic AGM θ functions. A128640

Expansion of r(q)⁴ / r(q⁴) in powers of q where r() is the Rogers-Ramanujan continued fraction. A285629

G.f. satisfies A(x) = 1 + x·A(x) / (1 + x·A(x)⁴). A364737

Expansion of (∏_j>=1 (1-(-x)^j) - 1)¹⁴ in powers of x. A47639

Difference between sums of quadratic residues and non-residues modulo n that are coprime to n. A255643

G.f.: ∑_n>=0 (x^2·n-1 + 1)ⁿ * xⁿ / (1 + x^2·n+1)ⁿ⁺¹, an even function. A326602