Properties of the Number 19821

Nineteen Thousand Eight Hundred Twenty-One

Basics

Value: 19820 → 19821 → 19822

Parity: odd

Prime: No

Previous Prime: 19819

Next Prime: 19841

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 3 × 6607

Divisors: 1, 3, 6607, 19821

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

8509 Try Today's Challenge

Representations

Binary: 100110101101101

Octal: 46555

Duodecimal: B579

Hexadecimal: 4d6d

Square: 392872041

Square Root: 140.78707327024026

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

Rotating digits of a(n)² right once still yields a square. A45877

Expansion of 1/sqrt((1-x)²-8x³). A98480

Expansion of 1/((1-x)(1-4x)(1-5x)(1-8x)). A21764

a(n) = 4·a(n-1) + 9·a(n-2), for n>1, with a(0)=1, a(1)=3. A122120

"Early bird" squares: write the square numbers in a string 149162536496481100... . Sequence gives numbers k such that k² occurs in the string ahead of its natural place. A181585

Number of nXnXn 0..6 triangular arrays with each element·equal to the number its neighbors equal to 6,0,0,0,0,0,1 for x=0,1,2,3,4,5,6. A203201

a(n) = 1+∑_k=1..2ⁿ-1 A000010(k). A255541

Decimal expansion of sine of 12 degrees. A19821