Properties of the Number 21281

Twenty-One Thousand Two Hundred Eighty-One

Basics

Value: 21280 → 21281 → 21282

Parity: odd

Prime: No

Previous Prime: 21277

Next Prime: 21283

Digit Sum: 14

Digital Root: 5

Palindrome: No

Factorization: 13 × 1637

Divisors: 1, 13, 1637, 21281

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001100100001

Octal: 51441

Duodecimal: 10395

Hexadecimal: 5321

Square: 452880961

Square Root: 145.8800877433243

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*(n²+3·n-1)/3. A84990

T(n,k)=Number of length n+3 0..k arrays with some pair in every consecutive four terms totalling exactly k. A245950

Semiprimes that are the sum of the first n semiprimes for some n. A92190

Fundamental discriminants d uniquely characterizing all complex biquadratic fields Q(sqrt(-3),sqrt(d)) which have 3-class group of type (3,3) and second 3-class group isomorphic to SmallGroup(729,34). A250241

Positive integers of the form (10·m²+1)/11. A179338

a(n) = 29 + 73·n + 37·n². A145980

Partial sums of A256970. A256971

Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n) - n, where a(0) = 1, a(1) = 2, b(0) = 3, b(1) = 4, b(2) = 5, and (a(n)) and (b(n)) are increasing complementary sequences. A296557

a(n) = a(n-1) + a(n-2) + 1, with a(0) = 1 and a(1) = 6. A22320

Number of 5-element families of an n-element set such that every 4 members of the family have a nonempty intersection. A51367