9081
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
- 1
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 13130
- Proper Divisor Sum (Aliquot Sum)
- 4049
- 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
- 6048
- Möbius Function
- 0
- Radical
- 3027
- 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
- 96
- 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
- (s(n)+1)/10, where s(n)=n-th base 10 palindrome that starts with 9.at n=30A043088
- Number of n-digit 7-smooth numbers (A002473).at n=16A085630
- The two digits touching the first comma have as absolute difference 0. The next such difference is 1. The next one is 2. Then 3, 4, 5... etc. When we reach 9 the differences start a new cycle: 0, 1, 2, 3... etc. Among many such possible sequences, this is the slowest increasing one starting with "1".at n=48A098795
- Triangle, read by rows, where T(n,k) equals the dot product of the vector of terms in row n that are to the right of T(n,k) with the vector of terms in column k that are above T(n,k): T(n,k) = Sum_{j=0..n-k-1} T(n,j+k+1)*T(j+k,k) for n > k+1 > 0, with T(n,n) = 1 and T(n,n-1) = n (n>=1).at n=28A115080
- Column 0 of triangle A115080.at n=7A115081
- Number of partitions of n with even crank.at n=36A124227
- Number of 4-noncrossing RNA structures with arc-length => 4.at n=11A140639
- Numbers k which can be split into two numbers x and y such that x^3 + y^2 is a multiple of k.at n=29A162451
- G.f.: A(x) = exp( Sum_{n>=1} A163659(n)^2*x^n/n ), where x*exp(Sum_{n>=1} A163659(n)*x^n/n) = S(x) is the g.f. of Stern's diatomic series (A002487).at n=14A163658
- Number of binary strings of length n with equal numbers of 00010 and 10010 substrings.at n=14A164221
- Number of -n..n circular arrays x(0..4) of 5 elements with zero sums of x(i) and x(i)*x((i+1) mod 5).at n=43A202007
- Number of n X 4 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 1 0 1 vertically.at n=9A207165
- a(n) = Sum_{i=0..n} digsum_4(i)^3, where digsum_4(i) = A053737(i).at n=65A231666
- Number of partitions of n containing m(3) as a part, where m denotes multiplicity.at n=37A240488
- Number of compositions of n in which the maximal multiplicity of parts equals 8.at n=10A243125
- Number of balanced ternary words of length n.at n=20A260938
- Numbers k such that 4*10^k + 19 is prime.at n=25A271548
- p-INVERT of (1,0,0,1,0,0,1,0,0,...), where p(S) = (1 - S)^2.at n=19A289919
- Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-2) + n -1, where a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4.at n=15A293351
- Where the zeros in A123066 occur.at n=33A321962