8205
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 13152
- Proper Divisor Sum (Aliquot Sum)
- 4947
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 4368
- Möbius Function
- -1
- Radical
- 8205
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- 39
- 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
- no
- Odd
- yes
Appears in sequences
- Expansion of 1/((1-x^2)*(1-x^4)^2*(1-x^6)*(1-x^8)*(1-x^10)) (even powers only).at n=39A001994
- a(n) = 2^n + n.at n=13A006127
- a(n+1) = [ A*a(n)+B ]/p^r, where p^r is the highest power of p diving [ A*a(n)+B ] and p=2, A=2.00013, B=3.0.at n=19A029580
- a(n+1) = a(n)-th composite and a(1) = 13.at n=29A059408
- Numbers n such that p = n^2 + 2, p+2 and p+6 are consecutive primes.at n=18A086380
- Number of rules of a context-free grammar in Chomsky normal form that generates all permutations of n symbols.at n=8A090328
- a(n) = (3/2)*(1/p)*(2*p+1)*(3^p+1)*B(2*p) where p = prime(n) and where B(k) denotes the k-th Bernoulli number.at n=1A090823
- Numbers n such that the partition function A000041(k) is even and odd the same number of times for 0 <= k <= n.at n=25A098936
- Nonprimes k such that 3^k == 3 (mod k).at n=27A122780
- Terms of A122780 which are not Carmichael numbers A002997.at n=21A153514
- Sums of three Mersenne primes.at n=22A174055
- Where powers of 2 occur in the union of squares and powers of 2.at n=26A188917
- Numbers 1 through 10000 sorted lexicographically in binary representation.at n=36A190126
- Expansion of x*(1+x)/(1-x-2*x^2-2*x^3-x^4).at n=11A210460
- a(n) = floor((5^n+1)/(2*3^n)).at n=18A238777
- a(n) = 2^prime(n) + prime(n).at n=5A243139
- Triangle read by rows: T(n,k) is the coefficient A_k in the transformation Sum_{k=0..n} (k+1)*x^k = Sum_{k=0..n} A_k*(x+2)^k.at n=40A246788
- Numbers n such that a digit of n to the power k plus the sum of the other digits of n equals n, where k is a positive integer.at n=13A257860
- Permutation of natural numbers: a(1) = 0, after which, a(2n) = A087686(1+a(n)), a(2n+1) = A088359(a(A268674(2n+1))).at n=42A269852
- Alphabetically first list of self-describing statements about the letter-type content of the list itself.at n=48A271642