16905
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
- 24
- Divisor Sum
- 32832
- Proper Divisor Sum (Aliquot Sum)
- 15927
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7392
- Möbius Function
- 0
- Radical
- 2415
- Omega Function (Ω)
- 5
- 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
- 58
- 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 unrooted triangulations of a pentagon with n internal nodes.at n=6A005501
- Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 52.at n=4A031730
- Numbers whose base-7 representation contains exactly four 0's.at n=19A043396
- Odd numbers k such that the number of 1's in binary representation of k equals omega(k), the number of distinct primes in the factorization of k.at n=24A071595
- Values of n for which A095777(n) is 16 (those terms which are expressible in decimal digits for bases 2 through 17, but not for base 18).at n=15A095785
- a(n) = 25*n^2 + 5.at n=25A158445
- Number of spanning trees in G X P_n, where G = {{1, 2}, {1, 3}, {1, 4}, {1, 5}, {2, 3}, {2, 4}, {3, 5}}.at n=1A167063
- Array T(n,k) read by antidiagonals: T(n,k) is the number of [n,k]-triangulations in the plane, n >= 0, k >= 0.at n=42A169808
- 7 times hexagonal numbers: a(n) = 7*n*(2*n-1).at n=35A195320
- Number of nXnXn 0..6 triangular arrays with each element x equal to the number its neighbors equal to 4,1,1,1,2,0,0 for x=0,1,2,3,4,5,6.at n=4A198022
- Triangular array read by rows: T(n,k) is the number of forests of rooted trees on n labeled nodes with exactly k isolated nodes; n>=0, 0<=k<=n.at n=30A219034
- Expansion of F(x^2, x) where F(x,y) is the g.f. of A239927.at n=73A239928
- Expansion of Product_{k>=1} (1 + x^k) * (1 + x^(2*k)) * (1 + x^(3*k)) * (1 + x^(4*k)) * (1 + x^(5*k)).at n=30A327047
- a(n) is the least integer k such that sigma(k)/(d(k)*sopf(k)) = n where d=A000005, sigma=A000203 and sopf=A008472.at n=35A328174
- Odd numbers k such that sigma(k^2) > 2*k^2 and A003415(sigma(k^2)) < k^2.at n=39A347891
- Odd numbers k such that sigma(k) + sigma(k+2) > 2*sigma(k+1); odd terms in A053228.at n=38A358395
- Triangle read by rows: T(n,k) is the number of n-node connected unsensed planar maps with an external face and k triangular internal faces, n >= 3, 1 <= k <= 2*n - 5.at n=78A378103
- Numbers that can be written in exactly two different ways as s_1^x_1 + ... + s_t^x_t, with 1 < s_1 < ... < s_t and {s_1,..., s_t} = {x_1,..., x_t} for some t > 0.at n=41A386966
- Numbers k such that sigma(k) = psi(k) + tau(k)^2.at n=25A390296