Properties of the Number 21007

Twenty-One Thousand Seven

Basics

Value: 21006 → 21007 → 21008

Parity: odd

Prime: No

Previous Prime: 21001

Next Prime: 21011

Digit Sum: 10

Digital Root: 1

Palindrome: No

Factorization: 7 × 3001

Divisors: 1, 7, 3001, 21007

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101001000001111

Octal: 51017

Duodecimal: 101A7

Hexadecimal: 520f

Square: 441294049

Square Root: 144.93791774411554

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

Numbers n such that uphi(n) = uphi(n+1), where uphi(n) is the unitary totient function (A047994). A287055

T(n,k)=Number of nXk 0..1 arrays with every element unequal to 2, 3, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. A320364

Numbers k such that iphi(k) = iphi(k+1), where iphi(k) is an infinitary analog to the Euler totient function (A091732). A326403

Record values in A317826. A317828

E.g.f. satisfies A(x) = exp(x * (1 + x)/A(x)). A365038

a(n) is the row of the Trithoff (tribonacci) array that contains the tails of the sequence which is n times the tribonacci numbers. A351685

"Real rabbits": a(n) = Re(c(n)) where complex c(n) = a(n) + i·b(n) and c(0) = i, c(1) = -i, c(n) = c(n-1) + i·c(n-2). A58184

Number of n X n symmetric 0..6 arrays with rows, considered as 7-ary numbers, in nondecreasing order. A162082

Number of (n+2)X(n+2) 0..2 arrays with every 3X3 subblock commuting with each horizontal and vertical neighbor 3X3 subblock. A186559

Number of (n+2) X 7 0..2 arrays with every 3 X 3 subblock commuting with each horizontal and vertical neighbor 3 X 3 subblock. A186564