Properties of the Number 21409

Twenty-One Thousand Four Hundred Nine

Basics

Value: 21408 → 21409 → 21410

Parity: odd

Prime: No

Previous Prime: 21407

Next Prime: 21419

Digit Sum: 16

Digital Root: 7

Palindrome: No

Factorization: 79 × 271

Divisors: 1, 79, 271, 21409

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101001110100001

Octal: 51641

Duodecimal: 10481

Hexadecimal: 53a1

Square: 458345281

Square Root: 146.31814651641812

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 compositions of n whose leaders of strictly decreasing runs are distinct. A374761

a(n) = a(1) + a(2) + ... + a(n-1) + a(m) for n >= 4, where m = 2·n - 2 - 2^p+1 and p is the unique integer such that 2^p < n-1 <= 2^p+1, with a(1) = a(2) = 1 and a(3) = 2. A49939

Counterbalanced numbers: Composite numbers k such that φ(k)/(σ(k)-k) is an integer. A55940

Numbers with two or more distinct prime factors such that the number and all its prime factors fall on a single straight line when they are plotted on a square spiral. A346294

Number of partitions of 9·n-8 into parts having in decimal representation digital root 1. A156145

Numbers k such that 105·2^k+1 is prime. A32402

Number of UH^jU's for some j>0, where U=(1,1) and H=(1,1), in all peakless Motzkin paths of length n (can be easily expressed using RNA secondary structure terminology). A187257

a(n) = ∑_{k=0..floor(n/4)} binomial(n+k,k) * binomial(n-3·k,k). A383529

Partial sums of squares of Catalan numbers (A000108). A94639

Decimal expansion of 1/405. A21409