15009
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 20016
- Proper Divisor Sum (Aliquot Sum)
- 5007
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10004
- Möbius Function
- 1
- Radical
- 15009
- 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
- 115
- Smith Number
- no
- Vampire 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
Appears in sequences
- a(n) = Sum{a(k): k=0,1,2,...,n-4,n-2,n-1}; a(n-3) is not a summand; initial terms are 0,1,4.at n=16A049860
- Numerators of expansion of a function eta(x) related to Cremer points.at n=21A058969
- Sum of GCD's of parts in all partitions of n.at n=34A078392
- Composite numbers, not ending with 0, sharing a 3-digit sequence with some of its prime factors.at n=14A131523
- L.g.f.: Sum_{n>=1} (Sum_{d|n} d*x^d)^n/n = Sum_{n>=1} a(n)*x^n/n.at n=11A192859
- a(n) is the sum of all distinct integers that can be produced by reversing the digits of n in any base b >= 2.at n=52A211518
- Equals two maps: number of nX2 binary arrays indicating the locations of corresponding elements equal to exactly two of their king-move neighbors in a random 0..1 nX2 array.at n=11A220243
- Number of ways to reciprocally link elements of an n X 2 array either to themselves or to exactly two king-move neighbors.at n=6A220590
- T(n,k) = Number of ways to reciprocally link elements of an n X k array either to themselves or to exactly two king-move neighbors.at n=29A220595
- T(n,k) = Number of ways to reciprocally link elements of an n X k array either to themselves or to exactly two king-move neighbors.at n=34A220595
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 870", based on the 5-celled von Neumann neighborhood.at n=36A273705
- Solution (a(n)) of the complementary equation a(n) = 2*a(n-1) - a(n-2) + b(n-1) + b(n); see Comments.at n=32A305330
- Expansion of 1 / Sum_{k>=0} (-x)^(k*(3*k - 1)/2).at n=39A308806