7155
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
- 16
- Divisor Sum
- 12960
- Proper Divisor Sum (Aliquot Sum)
- 5805
- 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
- 3744
- Möbius Function
- 0
- Radical
- 795
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 75
- 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
- Number of n-bead necklaces (turning over is allowed) where complements are equivalent.at n=19A000011
- MacMahon's generalized sum of divisors function.at n=35A002127
- Number of self-dual 2-colored necklaces with 2n beads.at n=18A007147
- a(n) = floor( n*(n-1)*(n-2)/22 ).at n=55A011904
- [ n(n-1)(n-2)(n-3)/13 ].at n=19A011923
- Number of triples of different integers from [ 2,n ] with no global factor.at n=37A015618
- a(1) = 2; a(n+1) = a(n)-th composite.at n=30A022450
- Sum{T(i,j)}, 0<=i<=n, 0<=j<=n, T given by A026659.at n=11A026668
- Numbers n such that n divides the (right) concatenation of all numbers <= n written in base 19 (most significant digit on right).at n=25A029512
- "DGK" (bracelet, element, unlabeled) transform of 2,1,1,1,...at n=27A032232
- Composite numbers whose prime factors contain no digits other than 3 and 5.at n=42A036315
- Triangle read by rows: T(n, k) = [x^k] x*Pochhammer(n + x, n)/(n + x).at n=17A038455
- Third column of Jabotinsky-triangle A038455 related to A006963.at n=3A039646
- Third unsigned column of triangle A051339.at n=5A051546
- Larger members of g-reduced amicable pairs a < b such that sigma(a) = sigma(b) = a + b + gcd(a,b).at n=24A054572
- Numbers n such that n | sigma_13(n).at n=19A055717
- Beginning with 1, minimum value such that gcd(a(2n-1),a(2n)) = 1, gcd(a(2n),a(2n+1))>1 and a(n) > a(n-1).at n=47A091856
- Bisection of A000011.at n=9A092668
- a(n) = Sum_{i=1..n} A005235(i).at n=44A097589
- a(n) = a(n-2)+a(n-3)+a(n-4)+a(n-5)+a(n-6)+2*a(n-7)+a(n-8).at n=23A109540