8217
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
- 2
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 13104
- Proper Divisor Sum (Aliquot Sum)
- 4887
- 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
- 4920
- Möbius Function
- 0
- Radical
- 2739
- Omega Function (Ω)
- 4
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 158
- 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
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)*Pi*n^(3/2), P(n) = A(n) - V(n); A000092 gives values of n where |P(n)| sets a new record; sequence gives A(A000092(n)).at n=12A000413
- Centered icosahedral (or cuboctahedral) numbers, also crystal ball sequence for f.c.c. lattice.at n=13A005902
- Let j = | i - i_written_backwards |, k = j + j_written_backwards; then k is in this sequence.at n=38A008920
- a(n) = a(n-1) + a(n-2) + 1, with a(0)=3, a(1)=10.at n=15A022409
- a(n) = (d(n)-r(n))/2, where d = A026043 and r is the periodic sequence with fundamental period (1,1,0,0).at n=33A026044
- 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=25A029580
- a(n) = n-th prime number * n-th lucky number.at n=22A032601
- Closed 3-dimensional ball numbers (version 1): a(n)= number of integer points (i,j,k) contained in a closed ball of diameter n, centered at (0,0,0).at n=25A053591
- Open 3-dimensional ball numbers (version 1): a(n) is the number of integer points (i,j,k) contained in an open ball of diameter n, centered at (0,0,0).at n=25A053592
- a(n) = n^2 + (n^2 with digits reversed).at n=36A061226
- a(n) = 2^n + 2*n - 1.at n=13A061761
- Integer part of log(n!)^log(n).at n=14A062421
- Nearest integer to log(n!)^log(n).at n=14A062422
- a(n) = min( x : x^3 + n^3 == 0 mod (x+n-1) ).at n=52A066486
- Start with Pascal's triangle; form a triangle by sliding down n steps from top on both sides and including the horizontal row, deleting the inner numbers; a(n) = sum of entries on perimeter of triangle.at n=13A081494
- Triangle read by rows: T(n,k) is the number of Dyck paths of semilength n, having k long ascents (i.e., ascents of length at least 2). Rows are of length 1,1,2,2,3,3,... .at n=47A091156
- a(n) = 3*(2*n^2 + 1).at n=37A097803
- Numbers n such that the partition function A000041(k) is even and odd the same number of times for 0 <= k <= n.at n=30A098936
- Number of complete compositions of n.at n=14A107429
- Numbers k such that k + sigma(k) is a triangular number.at n=38A115904