7731
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 11180
- Proper Divisor Sum (Aliquot Sum)
- 3449
- 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
- 5148
- Möbius Function
- 0
- Radical
- 2577
- Omega Function (Ω)
- 3
- 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
- 145
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
Appears in sequences
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 87.at n=18A031585
- Floor( 7*n^2/2 ).at n=47A032525
- Numbers m such that the factorizations of m..m+3 have the same number of primes (including multiplicities).at n=35A045940
- Number of partitions of n with equal nonzero number of parts congruent to each of 0, 2 and 3 (mod 4).at n=54A046780
- Number of trees with n nodes and 4 leaves.at n=32A055291
- Dimension of the space of weight n cuspidal newforms for Gamma_1( 71 ).at n=37A063344
- Index of the primes in A084163.at n=12A084164
- Number of bridged bicyclic skeletons with n carbon atoms (see Parks et al. for precise definition).at n=9A121333
- Numbers n such that n, n+1, n+2 and n+3 are products of exactly 3 primes.at n=33A124057
- Triangle T, read by rows, where the g.f. of column k in matrix power T^m is given by: 1/(1-x)^m = Sum_{n>=k} [T^m](n,k) * x^(n-k)/(1+x)^{n(n-1)/2 - k(k-1)/2} for k>=0.at n=60A141760
- Number of n X n binary arrays, symmetric under 180 degree rotation, with every 1 adjacent to at least one other 1 both bishopwise and rookwise but with no three 1s in a row bishopwise or rookwise.at n=7A144244
- Number of binary strings of length n with no substrings equal to 0001, 0110, or 1110.at n=25A164482
- Numbers n such that 4n + 1, 4n + 2 and 4n + 3 are not squarefree.at n=16A258332
- a(n) is the number of ways to select an ordered pair of subsets of {2,...,n} such that each pair of elements from different subsets are relatively prime.at n=10A260185
- Intersection of A269315 and A269314.at n=29A269316
- Length of shortest prefix of the Kolakoski sequence K (A000002) containing all blocks of length n that appear in K.at n=33A283511
- Number of non-equivalent ways to tile an n X n X n triangular area with three 2 X 2 X 2 triangular tiles and an appropriate number (= n^2-12) of 1 X 1 X 1 tiles.at n=7A286445
- a(n) = a(n-1) + a(n-2) + a([n/2]), where a(0) = 1, a(1) = 1, a(2) = 1.at n=18A298338
- The number of vertices inside a cross with width 3 and height n (see Comments in A331455 for definition) formed by the straight line segments mutually connecting all vertices and all points.at n=13A330850
- E.g.f.: exp( (x * exp(-x) + sinh(x)) / 2 ).at n=10A346748