Properties of the Number 18721

Eighteen Thousand Seven Hundred Twenty-One

Basics

Value: 18720 → 18721 → 18722

Parity: odd

Prime: No

Previous Prime: 18719

Next Prime: 18731

Digit Sum: 19

Digital Root: 1

Palindrome: No

Factorization: 97 × 193

Divisors: 1, 97, 193, 18721

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: Yes

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 100100100100001

Octal: 44441

Duodecimal: AA01

Hexadecimal: 4921

Square: 350475841

Square Root: 136.82470537150812

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

Fermat pseudoprimes to base 2, also called Sarrus numbers or Poulet numbers. A1567

Triangular numbers (A000217) with prime indices. A34953

Pseudoprimes to base 3. A5935

Strong pseudoprimes to base 3. A20229

Numbers of the form p·q, p and q prime with q=2·p-1. A129521

Centered 24-gonal numbers. A69190

Triangular numbers which are the product of two primes. A68443

Super-Poulet numbers: Poulet numbers whose divisors d all satisfy d∣2^d-2. A50217

Pseudoprimes to base 7. A5938

Nonprimes k such that 3^k == 3 (mod k). A122780