Properties of the Number 21040

Twenty-One Thousand Forty

Basics

Value: 21039 → 21040 → 21041

Parity: even

Prime: No

Previous Prime: 21031

Next Prime: 21059

Digit Sum: 7

Digital Root: 7

Palindrome: No

Factorization: 2 ⁴ × 5 × 263

Divisors: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101001000110000

Octal: 51060

Duodecimal: 10214

Hexadecimal: 5230

Square: 442681600

Square Root: 145.05171491574995

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 integer partitions of n that are not pairwise coprime, where a singleton is not coprime unless it is (1). A335240

T(n,k) = 4·A046802(n,k) - 3·A007318(n,k), triangle read by rows (0 <= k <= n). A168289

Coefficients of polynomials described below. A174531

Expansion of ∏_m>=1 (1 - m·q^m)⁷. A22667

a(1)=1, a(n) = a(n-1) + n³ if n odd, a(n) = a(n-1) + n² if n is even. A140154

Nonprime numbers k whose arithmetic derivative k' (A003415) is a Fibonacci number (A000045). A362141

Expansion of e.g.f. exp(-2·x) / (1 - log(1 + x)). A368289

Alternating sum of the numbers in the trajectory of n for the 3x+1 problem. A386437

a(n) = Ann(2n) where Ann(n) is the number of annular non-crossing matchings with n total endpoints. A268042

Knight's tour on spirally numbered infinite board, when the knight always jumps on the unvisited square closest to the origin, first according to the sup-norm, then 2-norm, then number of the square: a(n) = number of square visited at move n. A328909