Properties of the Number 21028

Twenty-One Thousand Twenty-Eight

Basics

Value: 21027 → 21028 → 21029

Parity: even

Prime: No

Previous Prime: 21023

Next Prime: 21031

Digit Sum: 13

Digital Root: 4

Palindrome: No

Factorization: 2 ² × 7 × 751

Divisors: 1, 2, 4, 7, 14, 28, 751, 1502, 3004, 5257

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001000100100

Octal: 51044

Duodecimal: 10204

Hexadecimal: 5224

Square: 442176784

Square Root: 145.01034445859372

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

a(n) = ∑_m=1..n ∑_k=1..m prime(k). A14148

Number of non-connected simple labeled graphs covering n vertices. A327070

T(n,k)=Number of (n+2)X(k+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000011 or 00001001. A260294

T(n,k)=Number of nXk 0..2 arrays with no average of any element and its diagonal, antidiagonal, horizontal and vertical neighbors equal to one. A200809

Rounded volume of a regular dodecahedron with edge length n. A71401

Numbers k such that k·k! - 1 is prime. A90704

Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = ∑_j=0..n (-k)^n-j * j^j * binomial(n,j). A362856

Number of tilings of a 5 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles. A219969

Those terms of A255571 whose every A080541/A080542-rotation is also a term of A255571. A258001

a(n) = (2^p+1)^p-1 modulo p², where p is prime(n). A260531