13155
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
- 4
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 21072
- Proper Divisor Sum (Aliquot Sum)
- 7917
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7008
- Möbius Function
- -1
- Radical
- 13155
- Omega Function (Ω)
- 3
- 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
- 138
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- Number of partially labeled trees with n nodes (4 of which are labeled).at n=4A000485
- a(n) = 3*Catalan(n) - Catalan(n-1) - 1.at n=8A000781
- Triangle read by rows: T(n,k) is the number of partially labeled trees with n nodes, k of which are labeled, 0 <= k <= n.at n=40A034799
- Triangle of number of node labeled trees by number of nodes and number of labels.at n=32A034800
- Schoenheim bound L_1(n,n-5,n-6).at n=19A036837
- Number of partitions of n in which the sequence of frequencies of the summands is nondecreasing.at n=39A100883
- Odd winning positions in Fibonacci nim.at n=30A120904
- Fixed points of A075075.at n=10A185635
- Coefficient of x in the reduction by x^2->x+1 of the polynomial p(n,x) defined at Comments.at n=9A193047
- a(n) = (binomial(n,5) - floor(n/5)) / 5.at n=20A215052
- Sums of Pythagorean sextuples in increasing order: The sums of sets of six natural numbers which correspond to the lengths of the edges of a tetrahedron whose four faces are all different Pythagorean triangles.at n=17A248548
- Numbers of the form Bell(i)*Bell(j).at n=25A276281
- Number of strict compositions of n with no three consecutive parts in arithmetic progression.at n=27A325849
- The smallest number whose prime factor concatenation, as well as the number itself, when written in base n, contains all digits 0,1,...,(n-1).at n=4A373645
- Irregular triangle read by rows: T(n,k), n > 1 and k <= n, is the smallest composite number x whose set of digits and the set of digits in all prime factors of x, when written in base n, contain exactly k digits in common, or -1 if no such number exists.at n=24A374225
- a(n) is the number of distinct solution sets to the quadratic equations u*x^2 + v*x + w = 0 with integer coefficients u, v, w, abs(u) + abs(v) + abs(w) <= n having a negative discriminant.at n=40A381710
- Irregular triangle read by rows: T(n,k) is the number of non-isomorphic directed graphs reachable in k >= 0 steps (and no fewer) by n >= 1 agents using the ANY protocol (see A318154).at n=38A383386