Properties of the Number 21085

Twenty-One Thousand Eighty-Five

Basics

Value: 21084 → 21085 → 21086

Parity: odd

Prime: No

Previous Prime: 21067

Next Prime: 21089

Digit Sum: 16

Digital Root: 7

Palindrome: No

Factorization: 5 × 4217

Divisors: 1, 5, 4217, 21085

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 101001001011101

Octal: 51135

Duodecimal: 10251

Hexadecimal: 525d

Square: 444577225

Square Root: 145.2067491544384

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

Semiprimes in A056106. A113524

Number of consecutive runs of 3 odd nonprimes congruent to 3 mod 4 below 10ⁿ. A93188

Array read by antidiagonals: T(n,k) is the number of noncrossing k-gonal cacti with n polygons up to rotation. A361236

Expansion of ∏_k>=1 (1 + x^k) * (1 + x^2·k) * (1 + x^3·k) * (1 + x^4·k) * (1 + x^5·k). A327047

Number of ways to tile a hexagonal strip made up of 4·n equilateral triangles, using triangles and diamonds. A356622

Triangle, read by rows, T(n, k) = f(n,k,q) - f(n,0,q) + 1, where f(n, k, q) = [x^k](p(x,n,q)), p(x, n, q) = (1-x)ⁿ⁺¹*∑_{k >= 0} ( (q·k+1)ⁿ + (q*(k+1)-1)ⁿ )*x^k, and q = 2. A176198

Expansion of ∏_m>=1 (1 - m·q^m)⁵. A22665

a(n) is the number of 4 element sets of distinct integer sided strict rectangles that fill an n X n square. A384724

Conjectured least number k such that prime(n) is the largest divisor of k³ - 1, or 0 if there is no such k. A223706

Number of length 2+2 0..n arrays with the sum of medians of adjacent triples multiplied by some arrangement of +-1 equal to zero. A253130