Properties of the Number 687

Six Hundred Eighty-Seven

Basics

Value: 686 → 687 → 688

Parity: odd

Prime: No

Previous Prime: 683

Next Prime: 691

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 3 × 229

Divisors: 1, 3, 229, 687

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 1010101111

Octal: 1257

Duodecimal: 493

Hexadecimal: 2af

Square: 471969

Square Root: 26.210684844162312

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

Toothpick sequence (see Comments lines for definition). A139250

Number of elements in the set {(x,y): 1 <= x,y <= n, gcd(x,y)=1}. A18805

Number of compositions (ordered partitions) of n that are concave-down sequences. A70211

Partial sums of A299254. A299260

Sum of smallest parts of all partitions of n. A46746

Number of representations of n as a sum of products of positive integers. 1 is not allowed as a factor, unless it is the only factor. Representations which differ only in the order of terms or factors are considered equivalent. A66739

a(n) = 3·prime(n). A1748

Number of necklaces with n beads of 2 colors, allowing turning over (these are also called bracelets). A29

Numbers k whose largest divisor <= sqrt(k) is 3. A161345

Numbers m such that the Bernoulli number B_2·m has denominator 42. A51227