15906
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 34848
- Proper Divisor Sum (Aliquot Sum)
- 18942
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 4800
- Möbius Function
- 1
- Radical
- 15906
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 4
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
- 97
- 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
- yes
- Odd
- no
Appears in sequences
- Number of Hamiltonian cycles in C_4 X P_n.at n=7A003699
- Numbers k such that phi(k) + 2 | sigma(k + 2).at n=20A015781
- Numbers which are the sum of their proper divisors containing the digit 5.at n=26A059464
- Composite numbers k such that sigma(k)*(phi(k) + 2) is a square.at n=27A065655
- Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly one way.at n=10A076454
- Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.at n=4A163055
- G.f.: exp( Sum_{n>=1} 2*Pell(n)^2 * x^n/n ), where Pell(n) = A000129(n).at n=7A208034
- Number of (w,x,y,z) with all terms in {1,...,n} and w*x+y*z>n^2.at n=20A212136
- Generalized Markoff numbers: largest of 7-tuple of positive numbers a, b, c, d, e, f, g satisfying the Markoff(7) equation a^2+b^2+c^2+d^2+e^2+f^2+g^2 = 2abcdefg.at n=27A227210
- Expansion of (1+4*x+x^2)/((1+x)^2*(1-x)^5).at n=20A233329
- Series reversion of x*(1-3*x^2)/(1-x^2) in odd-order powers.at n=5A235347
- Number of partitions of n such that m(2) < m(3), where m = multiplicity.at n=42A240063
- Number of equivalence classes of two-layer networks on n channels modulo permutations.at n=19A244484
- a(n) = 15*n^2 - 13*n.at n=33A263226
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 629", based on the 5-celled von Neumann neighborhood.at n=23A273297
- a(n) = Sum_{k=0..n} Stirling2(n,k) * A000009(k) * k^k.at n=4A316146
- a(n) = Sum_{p | A055204(n)} 2^(pi(p) - 1).at n=45A336510
- Number of partitions of n into 6 or more distinct parts.at n=46A347573
- Array read by antidiagonals: T(n,k) is the number of Hamiltonian cycles in the stacked prism graph P_n X C_k, n >= 1, k >= 2.at n=52A359855
- G.f. satisfies A(x) = 1/(1-x)^3 + x^2*A(x)^2.at n=10A364625