Properties of the Number 21305

Twenty-One Thousand Three Hundred Five

Basics

Value: 21304 → 21305 → 21306

Parity: odd

Prime: No

Previous Prime: 21283

Next Prime: 21313

Digit Sum: 11

Digital Root: 2

Palindrome: No

Factorization: 5 × 4261

Divisors: 1, 5, 4261, 21305

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001100111001

Octal: 51471

Duodecimal: 103B5

Hexadecimal: 5339

Square: 453903025

Square Root: 145.96232390586277

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

a(n) = ∑_k=0..n C(n-k, floor(k/2)). A97333

Stirling transform of A001563: a(0) = 1 and a(n) = ∑_k=1..n Stirling2(n,k)*k·k! for n >= 1. A69321

Expansion of (1+x)(1+x²)/(1-x-x³). A3410

T(n,k)=Number of nXk binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally. A228683

Expansion of (1 - x²)/(1 - x - x³). A58278

Euler transform of A051064, the ruler function sequence for k=3. A173241

a(0) = 1, a(1) = 2, a(2) = 5; for n >= 3, a(n) = a(n-1) + 2·a(n-2) + a(n-3). A101399

Number of (17,11)-reverse multiples with n digits. A226916

Positions of the positive integers in the ordering of rational numbers as generated by the rules: 1 is in S, and if nonzero·is in S, then x+1 and -1/x are in S. (See Comments.) A226136

Sieve performed by successive iterations of steps where step m is: keep m terms, remove the next 3 and repeat; as m = 1,2,3,.. the remaining terms form this sequence. A112561