Properties of the Number 20689

Twenty Thousand Six Hundred Eighty-Nine

Basics

Value: 20688 → 20689 → 20690

Parity: odd

Prime: No

Previous Prime: 20681

Next Prime: 20693

Digit Sum: 25

Digital Root: 7

Palindrome: No

Factorization: 17 × 1217

Divisors: 1, 17, 1217, 20689

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101000011010001

Octal: 50321

Duodecimal: BB81

Hexadecimal: 50d1

Square: 428034721

Square Root: 143.83671297690307

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

T(n,k)=Number of nXk arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2. A221388

a(n) is the 2-adic valuation of 1 + 3*{the n-th iterate of 27 with A371094}. A372448

Integers k such that 2047·2^k - 1 is prime. A387927

Pseudoprimes to base 78. A20206

Number of 4X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2·n² (number of collections of 4 zero-sum 2-vectors with total modulus squared not more than 2·n², ignoring vector and component permutations). A192703

Number of nX6 arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2. A221386

Number of 3 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2. A221389

a(1) = 1; for n > 1, a(n) is the smallest positive integer that has not yet appeared which contains all the distinct digits of the sum of all previous terms a(1)..a(n-1). A368347

Number of perfect matchings in graph P₁₀ X P_n. A28472

Numbers of form 6 x² + 7 y². A20689