Properties of the Number 21005

Twenty-One Thousand Five

Basics

Value: 21004 → 21005 → 21006

Parity: odd

Prime: No

Previous Prime: 21001

Next Prime: 21011

Digit Sum: 8

Digital Root: 8

Palindrome: No

Factorization: 5 × 4201

Divisors: 1, 5, 4201, 21005

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001000001101

Octal: 51015

Duodecimal: 101A5

Hexadecimal: 520d

Square: 441210025

Square Root: 144.9310180741169

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

n such that A205592(n) > n. A205594

Number of partitions of n containing at least one part m-7 if m is the largest part. A212547

Terms as well as digits fit the even/even/odd pattern; this is the lexicographically earliest injective sequence with this property. A375305

Number of 0..n arrays x(0..4) of 5 elements with nondecreasing average value and 0..n occur with instance counts within one of each other. A200944

Base-8 palindromes that start with 5. A43025

T(n,k)=Number of 0..k arrays x(0..n-1) of n elements with nondecreasing average value and 0..k occur with instance counts within one of each other. A200942

Let q_k=p(p+2) be product of k-th pair of twin primes; sequence gives values of p such that (q_k)² > q_k-iq_k+i for all 1 <= i <= k-1. A21005