Properties of the Number 20191

Twenty Thousand One Hundred Ninety-One

Basics

Value: 20190 → 20191 → 20192

Parity: odd

Prime: No

Previous Prime: 20183

Next Prime: 20201

Digit Sum: 13

Digital Root: 4

Palindrome: No

Factorization: 61 × 331

Divisors: 1, 61, 331, 20191

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2730 Try Today's Challenge

Representations

Binary: 100111011011111

Octal: 47337

Duodecimal: B827

Hexadecimal: 4edf

Square: 407676481

Square Root: 142.0950386185246

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(n,k)=Number of nXk 0..4 arrays with each element·equal to the number of its horizontal and vertical neighbors equal to 4,3,1,0,2 for x=0,1,2,3,4. A196904

Numbers k such that the digits of k² are exactly the same (albeit in different order) as the digits of (k+1)². A72841

G.f.: ∑_n>=0 (2 + xⁿ)ⁿ * xⁿ / (1-x)ⁿ⁺¹. A244615

Numbers k such that 2^2k-1 == 2 (mod 2k) and such that 2^k-1 ≠ 1 (mod k). A176033

Strong pseudoprimes to base 75. A20301

Strong pseudoprimes to base 83. A20309

Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 33 ones. A31801

a(n) = (2·n+1)*(11·n+1). A33575

Number of nX4 0..4 arrays with each element·equal to the number its horizontal and vertical neighbors equal to 4,3,1,0,2 for x=0,1,2,3,4. A196900

Number of nX6 0..4 arrays with each element·equal to the number its horizontal and vertical neighbors equal to 4,3,1,0,2 for x=0,1,2,3,4. A196902