12181
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 13132
- Proper Divisor Sum (Aliquot Sum)
- 951
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 11232
- Möbius Function
- 1
- Radical
- 12181
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 37
- 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
- Define C(n) by the recursion C(0) = 5*i where i^2 = -1, C(n+1) = 1/(1 + C(n)), then a(n) = 5*(-1)^n/Im(C(n)) where Im(z) denotes the imaginary part of z.at n=8A069962
- Scale factor by which primitive Pythagorean triangle {x=A088509(n), y=A088510(n), z=A088511(n)} needs be enlarged in order to circumscribe the smallest integral square having a side on the hypotenuse.at n=14A088544
- a(n) = 3^n *n! *L_{n}^{-1/3}(-1), where L_n^{alpha}(x) are generalized Laguerre polynomials.at n=4A089914
- Triangle read by rows: T(n,k) is the number of k-matchings in the P_4 X P_n lattice graph.at n=33A100265
- Expansion of 1/(1-x-3*x^2-4*x^3-2*x^4).at n=10A124861
- a(0) = a(1) = 1. a(n) = a(n-1) + a(n - b(n)), where b(n) is largest prime dividing n.at n=35A137809
- a(n) = 1 + n*(n+1)*(n-1)/2.at n=29A158842
- Centered 28-gonal numbers.at n=29A195314
- Beach-Williams Pell numbers of type pq (p,q primes).at n=9A212078
- Numbers k such that 2*k!! - 1 is prime.at n=35A215779
- a(n) = (15*n^2 + 9*n + 2)/2.at n=40A220083
- Number of compositions of n having exactly six fixed points.at n=13A240741
- T(n,k)=Number of nXk 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 0, 1 or 4 neighboring 1s.at n=46A297682
- Consider a square drawn on the perimeter of a square lattice with side length n. a(n) is the number of regions inside the square after drawing unit circles centered at each interior lattice point of the square.at n=42A339623
- G.f. A(x) satisfies: 1 - x = Sum_{n>=0} (x^(5*n) + (-1)^n*A(x))^n.at n=26A352821
- Number T(n,k) of partitions of n into k parts where each block of part i with multiplicity j is marked with a word of length i*j over an n-ary alphabet whose letters appear in alphabetical order and all n letters occur exactly once in the partition; triangle T(n,k), n>=0, 0<=k<=n, read by rows.at n=60A364310
- Number of partitions of 2n into n parts where each block of part i with multiplicity j is marked with a word of length i*j over a (2n)-ary alphabet whose letters appear in alphabetical order and all 2n letters occur exactly once in the partition.at n=5A364323
- Centered 30-gonal numbers.at n=28A389799
- Expansion of e.g.f. Series_Reversion(log(1+x) - x^3).at n=5A391954