9018
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
- 16
- Divisor Sum
- 20160
- Proper Divisor Sum (Aliquot Sum)
- 11142
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 2988
- Möbius Function
- 0
- Radical
- 1002
- Omega Function (Ω)
- 5
- Little Omega Function (ω)
- 3
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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 140
- 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
- yes
- Odd
- no
Appears in sequences
- Number of points on surface of truncated cube: a(n) = 46*n^2 + 2 for n > 0.at n=14A005911
- Number of 3 X n binary matrices with distinct rows, up to row and column permutation; (n,3)-hypergraphs (including empty hyperedge but excluding multiple hyperedges).at n=10A055194
- Numbers k such that k | sigma_9(k) - phi(k)^9.at n=22A055703
- Numbers k such that the k-th term of the EKG sequence (A064413(k)) has more than one controlling prime.at n=36A073735
- Least nontrivial multiple of the n-th prime beginning with 9.at n=38A078293
- p such that p^4 + q^4 = r^4 + s^4 = a(n).at n=26A088728
- 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=41A098795
- Multiples of 18 containing a 18 in their decimal representation.at n=20A121038
- a(0)=0, a(1)=1; and a(n) = a(n-1) + a(a(n-1) mod n) for n>=2.at n=44A125204
- G.f.: A(x) = Product_{n>=1} [ (1-x)^2*(1 + 2x + 3x^2 +...+ n*x^(n-1)) ].at n=25A129355
- a(n) = (sum of first n primes) * n.at n=17A167214
- G.f.: A(x) = Sum_{n>=0} x^(n^2) / Product_{k=1..n} (1 - x^k)^n.at n=23A193197
- Number of 2 X 2 matrices M of positive integers such that permanent(M) < n.at n=41A212151
- Total number of parts of multiplicity 9 in all partitions of n.at n=40A222709
- Numbers n such that A = n - digitsum(n) is divisible by the largest power of 10 <= A.at n=37A242474
- Natural numbers n that have the property that starting from k = n, the fixed point of the map k -> floor(tan(k)) is strictly positive, while the smallest number encountered during the iteration is strictly negative.at n=56A258202
- Smallest m such that A259043(m) = n.at n=43A259046
- Numbers n such that n*2^1279 - 1 is prime.at n=21A265502
- Numbers n such that Bernoulli number B_{n} has denominator 798.at n=37A272138
- Number of integers m, 1 <= m <= A002569(n), that are not terms in the triangle T(n,k) of A008284.at n=45A292994