Properties of the Number 21868

Twenty-One Thousand Eight Hundred Sixty-Eight

Basics

Value: 21867 → 21868 → 21869

Parity: even

Prime: No

Previous Prime: 21863

Next Prime: 21871

Digit Sum: 25

Digital Root: 7

Palindrome: No

Factorization: 2 ² × 7 × 11 × 71

Divisors: 1, 2, 4, 7, 11, 14, 22, 28, 44, 71

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101010101101100

Octal: 52554

Duodecimal: 107A4

Hexadecimal: 556c

Square: 478209424

Square Root: 147.87832836490952

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

Row 3 of A007754. A58794

Union_{odd primes p, n >= 3} {T_p(n)}, where T_m(x) = x·T_m-1(x) - T_m-2(x), m >= 2, T₀(x) = 2, T₁(x) = x (dilated Chebyshev polynomials of the first kind). A299071

a(n) = n³ - 3·n. A121670

a()=A037260 and its first [ A037261 ], 2nd [ A037262 ] and 3rd [ A037263 ] differences together include every number at most once and are monotonic and minimal. A37260

Number of partitions p of n such that 2*(number of even numbers in p) <= (number of odd numbers in p). A241652

Ulam's spiral (NNW spoke). A143860

a(n) = 28a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 28. A90249

Numerators of continued fraction convergents to sqrt(780). A42504

Sum of the k-th arithmetic derivative of n-k for k=0..n. A258652

Integers k equal to the sum over A024816(t) mod t, for some steps, starting with t = k and then using the result to feed the next calculation. A377002