17687
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 29
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18480
- Proper Divisor Sum (Aliquot Sum)
- 793
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 16896
- Möbius Function
- 1
- Radical
- 17687
- 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
- 79
- 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) = b(n) - c(n) where b(n) is the n-th Fibonacci number greater than 2 and c(n) is the n-th number not in sequence b( ).at n=18A014251
- a(n) = (-1)^(n+1)/5 * Sum_{k=1..2n} binomial(2n+1,k)*B(k)*5^k where B(k) are the Bernoulli numbers.at n=3A069990
- Maximum number of nonempty subtrees of a binary tree with n leaves.at n=10A092781
- Maximum possible number of subtrees of an n-node unrooted tree in which each node has maximum degree three (equivalently, rooted binary trees in which some internal nodes may have only one child). A subtree is a nonempty contiguous set of nodes, not necessarily including all descendants of the root.at n=21A124454
- Number of n X n symmetric 0..5 arrays with each element equal to at least one horizontal or vertical neighbor and any new values 0..5 introduced in lower triangular row major order.at n=4A192642
- Number of n X n symmetric 0..6 arrays with each element equal to at least one horizontal or vertical neighbor and any new values 0..6 introduced in lower triangular row major order.at n=4A192643
- Number of n X n symmetric 0..7 arrays with each element equal to at least one horizontal or vertical neighbor and any new values 0..7 introduced in lower triangular row major order.at n=4A192644
- Number of 0..n arrays x(0..4) of 5 elements with nondecreasing average value.at n=10A200765
- Partial sums of A175317 (Sum_{d|n} pod(d)).at n=19A280114
- Take a squarefree semiprime and take the difference of its prime factors. If it is a squarefree semiprime repeat the process. Sequence lists the squarefree semiprimes that generate other squarefree semiprimes only in the first k steps of this process. Case k = 4.at n=36A296811
- Odd composite integers m such that A004187(m-J(m,45)) == 0 (mod m) and gcd(m,45)=1, where J(m,45) is the Jacobi symbol.at n=31A340099
- Odd composite integers m such that A004187(2*m-J(m,45)) == J(m,45) (mod m) and gcd(m,45)=1, where J(m,45) is the Jacobi symbol.at n=39A340124