687
domain: N
Properties
Digital Properties
- Digit Count
- 3
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 920
- Proper Divisor Sum (Aliquot Sum)
- 233
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 456
- Möbius Function
- 1
- Radical
- 687
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- no
- Perfect Square
- no
- Perfect Cube
- no
- Pentagonal Number
- no
- Hexagonal Number
- no
- Lucas Number
- no
- Tetrahedral Number
- no
- Pell Number
- no
- Tribonacci Number
- no
- Pronic Number
- no
Recreational
- Happy Number
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 38
- Smith Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- Squarefree Number
- yes
- Prime Power
- no
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Names
- German
- sechshundertsiebenundachtzig· ordinal: sechshundertsiebenundachtzigste
- English
- six hundred eighty-seven· ordinal: six hundred eighty-seventh
- Spanish
- seiscientos ochenta y siete· ordinal: 687º
- French
- six cent quatre-vingt-sept· ordinal: six cent quatre-vingt-septième
- Italian
- seicentoottantasette· ordinal: 687º
- Latin
- sescenti octoginta septem· ordinal: 687.
- Portuguese
- seiscentos e oitenta e sete· ordinal: 687º
Appears in sequences
- Number of necklaces with n beads of 2 colors, allowing turning over (these are also called bracelets).at n=14A000029
- Number of nonnegative solutions to x^2 + y^2 <= n^2.at n=29A000603
- Numbers that are the sum of 4 cubes in more than 1 way.at n=38A001245
- a(n) = 3 * prime(n).at n=49A001748
- Number of integral points in a certain sequence of open quadrilaterals.at n=41A002578
- Representation degeneracies for Neveu-Schwarz strings.at n=16A005299
- Number of factorization patterns of polynomials of degree n over F_4.at n=12A006169
- Compositions: 6th column of A048004.at n=8A006980
- Low temperature antiferromagnetic susceptibility for honeycomb lattice.at n=8A007214
- Largest number not a sum of distinct primes >= prime(n).at n=46A007414
- Coordination sequence T1 for Zeolite Code ERI and OFF.at n=19A008093
- Coordination sequence T3 for Zeolite Code -WEN.at n=19A009864
- Coordination sequence T4 for Zeolite Code iRON.at n=19A009884
- Coordination sequence T2 for Zeolite Code VSV.at n=17A009915
- Antidiagonals of the prime-composite array B(m,n) (see A067681) that are zeros from the first Borve conjecture.at n=54A014617
- a(n+2) = 3*a(n) - a(n-2) with a(0) = 1, a(1) = 3, a(2) = 6.at n=10A018186
- Inverse Euler transform of A000931.at n=35A018243
- Number of elements in the set {(x,y): 1 <= x,y <= n, gcd(x,y)=1}.at n=32A018805
- a(n) = a(n-1) + c(n-1) for n >= 2, a( ) increasing, given a(1)=5; where c( ) is complement of a( ).at n=32A022937
- a(n) = a(n-1) + c(n-1) for n >= 2, a( ) increasing, given a(1)=6; where c( ) is complement of a( ).at n=32A022938