Properties of the Number 21405

Twenty-One Thousand Four Hundred Five

Basics

Value: 21404 → 21405 → 21406

Parity: odd

Prime: No

Previous Prime: 21401

Next Prime: 21407

Digit Sum: 12

Digital Root: 3

Palindrome: No

Factorization: 3 × 5 × 1427

Divisors: 1, 3, 5, 15, 1427, 4281, 7135, 21405

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001110011101

Octal: 51635

Duodecimal: 10479

Hexadecimal: 539d

Square: 458174025

Square Root: 146.30447703334303

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 length n+5 0..k arrays with every six consecutive terms having the maximum of some two terms equal to the minimum of the remaining four terms. A250081

Numbers divisible by prime(d) for each digit d in their base-9 representation, none of which may be zero. A256879

T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 0 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 0 3 4 6 or 7. A252105

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, starting with a(1) = 1, a(2) = 3, and a(3) = 2. A49923

Eigentriangle of Catalan triangle A033184. A172380

Numbers m that divide the alternating sum ∑_k=1..m (-1)^k+1 * usigma(k). A379924

Triangle whose inverse has production matrix with general term (-1)^n-k+1*C(k+1, n-k+1). A172381

Sum of prime anti-divisors of n = sum of prime anti-divisors of n+1 with n > 1. A192283

Number of length n+5 0..4 arrays with every six consecutive terms having the maximum of some two terms equal to the minimum of the remaining four terms. A250077

Number of length 2+5 0..n arrays with every six consecutive terms having the maximum of some two terms equal to the minimum of the remaining four terms. A250083