Properties of the Number 20898

Twenty Thousand Eight Hundred Ninety-Eight

Basics

Value: 20897 → 20898 → 20899

Parity: even

Prime: No

Previous Prime: 20897

Next Prime: 20899

Digit Sum: 27

Digital Root: 9

Palindrome: No

Factorization: 2 × 3 ⁵ × 43

Divisors: 1, 2, 3, 6, 9, 18, 27, 43, 54, 81

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000110100010

Octal: 50642

Duodecimal: 10116

Hexadecimal: 51a2

Square: 436726404

Square Root: 144.5614056378811

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 non-vanishing Feynman diagrams of order 2n for the vacuum polarization (the proper two-point function of the photon) and for the self-energy (the proper two-point function of the electron) in quantum electrodynamics (QED). A5412

Euler transform of reduced totient function ψ(n), cf. A002322. A61257

3 times 13-gonal (or tridecagonal) numbers: a(n) = 3·n*(11·n - 9)/2. A153875

Triangle read by rows: T(n,0) = 0 for n >= 0; T(n,2·k+1) = A152842(2·n,2*(n-k)) and T(n,2·k) = A152842(2·n,2*(n-k)+1) for n >= k > 0. A299989

A(n,k) is the sum over all Dyck paths of semilength n of products over all peaks p of (x_p+k·y_p)/y_p, where x_p and y_p are the coordinates of peak p; square array A(n,k), n>=0, k>=0, read by antidiagonals. A258219

Expansion of 1/(2 - ∏_k>=1 (1 + x^2·k-1)). A307058

Expansion of 1/(2 - ∏_k>=1 1/(1 + x^k)). A307060

Numbers on the square spiral board that are enclosed by four primes. A341542

Expansion of 1/(1 - x/(1 - 4·x)^1/2)³. A382540

Sequence of the "Natural Jewels": a natural jewel is a number that is totally enclosed by prime numbers in a version of Ulam Spiral. A172294