1638
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 24
- Divisor Sum
- 4368
- Proper Divisor Sum (Aliquot Sum)
- 2730
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 432
- Möbius Function
- 0
- Radical
- 546
- 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
- 42
- 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
- Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer.at n=7A001599
- Numbers k such that 5*2^k - 1 is prime.at n=20A001770
- a(n) = least value of m for which Liouville's function A002819(m) = -n.at n=44A002053
- Self numbers divisible by sum of their digits (or, self numbers which are also Harshad numbers).at n=38A003219
- Number of permutations of [n+1] with exactly 1 increasing subsequence of length 3.at n=5A003517
- a(n) = (6^n/n!) * Product_{k=0..n-1} (6*k + 7).at n=2A004997
- Number of non-vanishing Feynman diagrams of order 2n for the vacuum polarization (the proper two-point function of the photon) and for the self-energy (the proper two-point function of the electron) in quantum electrodynamics (QED).at n=4A005412
- a(n) is the number of Dyck paths of semilength n+6 having its first peak at height n+1.at n=5A005557
- Expansion of (1+x^2)/((1-x)^2*(1-x^2)^2).at n=25A005993
- From descending subsequences of permutations.at n=6A006220
- a(n) = n*(n+1)*(2*n+1)/3.at n=13A006331
- If n mod 2 = 0 then n*(n^2-4)/12 else n*(n^2-1)/12.at n=27A006584
- Numbers whose divisors' harmonic and arithmetic means are both integers.at n=5A007340
- Expansion of 1/((1-2*x)*(1+x^2)).at n=11A007910
- Coordination sequence T1 for Zeolite Code AET.at n=28A008007
- Coordination sequence T3 for Zeolite Code LIO.at n=28A008131
- Catalan triangle read by rows. Also triangle of expansions of powers of x in terms of Chebyshev polynomials U_n(x).at n=69A008315
- Dates of birth of Kings Louis I, II, ... of France.at n=13A008746
- Catalan's triangle T(n,k) (read by rows): each term is the sum of the entries above and to the left, i.e., T(n,k) = Sum_{j=0..k} T(n-1,j).at n=60A009766
- Numbers k such that k divides phi(k) * sigma(k).at n=50A011775