Properties of the Number 20661

Twenty Thousand Six Hundred Sixty-One

Basics

Value: 20660 → 20661 → 20662

Parity: odd

Prime: No

Previous Prime: 20641

Next Prime: 20663

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 3 × 71 × 97

Divisors: 1, 3, 71, 97, 213, 291, 6887, 20661

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000010110101

Octal: 50265

Duodecimal: BB59

Hexadecimal: 50b5

Square: 426876921

Square Root: 143.73934743138358

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

Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1), where a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4. A293358

The number of odd abundant numbers below 10ⁿ. A322287

Products p·q*r of three distinct primes such that (p·q) mod r, (p·r) mod q and (q·r) mod p are all prime. A338704

Number of nondecreasing arrays of n 0..n-1 integers with the sum of their 3rd powers equal to sum(i³,i=0..n-1). A216631

Lexicographically earliest increasing sequence of nonnegative numbers that contains no arithmetic progression of length 9. A20661

T(n,k)=Number of nondecreasing arrays of n 0..n-1 integers with the sum of their k'th powers equal to sum(i^k,i=0..n-1). A216635

a(n) = (1/5ⁿ) * ∑_k=0..n² ( (binomial(n², k) * 4^k) (mod 5ⁿ) ). A376534