Properties of the Number 21605

Twenty-One Thousand Six Hundred Five

Basics

Value: 21604 → 21605 → 21606

Parity: odd

Prime: No

Previous Prime: 21601

Next Prime: 21611

Digit Sum: 14

Digital Root: 5

Palindrome: No

Factorization: 5 × 29 × 149

Divisors: 1, 5, 29, 145, 149, 745, 4321, 21605

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010001100101

Octal: 52145

Duodecimal: 10605

Hexadecimal: 5465

Square: 466776025

Square Root: 146.98639392814562

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) = n*(n+1)*(5·n + 4)/6. A162147

Quintisection A061037(5·n+2). A165248

Number of toothpicks after n stages of 3-D toothpick structure defined in Comments. A170876

Permutation of natural numbers, a composition of A241909 and A064216: a(n) = A064216(A241909(n)). A243061

a(n) = (6·n+1)*(6·n+5). A1513

Number of partitions of n+3 with largest inscribed rectangle having area <= n. A218624

Second trisection of A061037. A142599

a(n) = prime(n)² - 4·prime(n). A245034

Nonprime numbers k of the form 4·m+1 such that ∑_j=0..k-1 2^j * binomial(3·j, j) == 1 (mod k). A373747

Primes p such that 2·p + 11 is a square. A269784