15840
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 72
- Divisor Sum
- 58968
- Proper Divisor Sum (Aliquot Sum)
- 43128
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 3840
- Möbius Function
- 0
- Radical
- 330
- Omega Function (Ω)
- 9
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 102
- 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
- Index of (the image of) the modular group Gamma(n) in PSL_2(Z).at n=32A001766
- Number of n-step walks on square lattice in the first quadrant which finish at distance n-3 from the x-axis.at n=29A005564
- Number of ordered quadruples of integers from [ 1..n ] with no global factor.at n=23A015634
- Binomial transform of Thue-Morse sequence A010060.at n=15A019302
- Theta series of A*_10 lattice.at n=31A023922
- a(n) = n!/LCM{1, C(n-1,1), C(n-2,2), ..., C(n-[ n/2 ],[ n/2 ])}.at n=11A025562
- a(n) = T(n,n-3), where T is the array in A026374.at n=29A026382
- Theta series of 10-d 11-modular Craig lattice A_10^(3).at n=11A028995
- A convolution triangle of numbers obtained from A036070.at n=24A030526
- Number of symmetrically inequivalent coincidence rotations of icosian ring of index n.at n=79A031366
- For all n, if d is recursively applied to a(n) exactly 6 times then the fixed point of d-iteration is just reached.at n=17A036458
- a(n) = n^2*(n-1)*(n-2).at n=10A047929
- E.g.f. (1-x)/(1-x-2x^2).at n=6A052598
- a(1) = 0, a(2) = 16, a(2n+1) = 10*a(2n) - a(2n-1), a(2n) = 10*a(2n-1) - a(2n-2) + 16.at n=4A053410
- a(1) = 1; for n>1, sum of binomial(n,k) as k runs over RRS(n), the reduced residue system of n.at n=14A056188
- Number of triangular regions in regular n-gon with all diagonals drawn.at n=30A062361
- a(n) = n! * Catalan(n+1).at n=5A065866
- Least m such that A067513(m) = n.at n=28A067846
- Numbers k such that k = phi(sigma(phi(sigma(phi(sigma(k)))))).at n=15A067884
- Numbers k such that k+1 is composite and divides 3^k-2^k.at n=31A068410