Properties of the Number 20780

Twenty Thousand Seven Hundred Eighty

Basics

Value: 20779 → 20780 → 20781

Parity: even

Prime: No

Previous Prime: 20773

Next Prime: 20789

Digit Sum: 17

Digital Root: 8

Palindrome: No

Factorization: 2 ² × 5 × 1039

Divisors: 1, 2, 4, 5, 10, 20, 1039, 2078, 4156, 5195

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101000100101100

Octal: 50454

Duodecimal: 10038

Hexadecimal: 512c

Square: 431808400

Square Root: 144.15269681833914

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

Number of ways to write n as an ordered sum of 5 squarefree numbers. A341065

G.f.: ∑_k>=0 x^k * ∏_j=1..5·k (1 + x^j). A385069

Increasing partial quotients in the continued fraction expansion of the prime constant (A051006). A102878

Denominators of continued fraction convergents to sqrt(751). A42447

Number of nX6 0..1 arrays with every element unequal to 0, 1, 2, 4, 6 or 8 king-move adjacent elements, with upper left element zero. A316302

a(n) = [x^n²] ∏_k=1..n theta₃(q^k), where theta₃() is the Jacobi θ function. A321179

G.f. A(x) satisfies A(x)³ = A( x³ + 3·x*A(x)³ + 3·A(x)⁵ ). A378263

Numbers n such that 179·2ⁿ-1 is prime. A50841

Expansion of ∏_j>=1 1/(1 + (-1 + ∏_k>=1 1/(1 + x^k))^j). A307438

Number of nXn 0..1 arrays with every element unequal to 0, 1, 2, 4, 6 or 8 king-move adjacent elements, with upper left element zero. A316298