Properties of the Number 21729

Twenty-One Thousand Seven Hundred Twenty-Nine

Basics

Value: 21728 → 21729 → 21730

Parity: odd

Prime: No

Previous Prime: 21727

Next Prime: 21737

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 3 × 7243

Divisors: 1, 3, 7243, 21729

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101010011100001

Octal: 52341

Duodecimal: 106A9

Hexadecimal: 54e1

Square: 472149441

Square Root: 147.40759817594207

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

Exponential generating function (1-x²)^-1/x. A121452

a(n) = number of primes of the form x² + 1 <= 2ⁿ. A83847

Odd numbers k such that φ(k) and cototient(k) have the same prime signature. A280927

Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 78 ones. A31846

Numbers k such that k and k² use only the digits 1, 2, 4, 7 and 9. A136998

Number of primes of the form x² + 1 < 2ⁿ. A174246

a(1)=1. a(n+1) = ∑_k=1..n a(b(k,n)), where b(k,n) is the largest positive integer that, when written in binary, occurs as a substring in both binary k and binary n. A175491

Number of nondecreasing arrangements of n+2 numbers in 0..8 with the last equal to 8 and each after the second equal to the sum of one or two of the preceding three. A190040

Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 98. A31596

Concatenation of first n taxicab numbers A011541. A132942