13215
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 21168
- Proper Divisor Sum (Aliquot Sum)
- 7953
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7040
- Möbius Function
- -1
- Radical
- 13215
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 169
- 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
- Becomes prime after exactly 7 iterations of f(x) = sum of prime factors of x.at n=29A047826
- Numbers n such that 93*2^n-1 is prime.at n=28A050572
- a(n) = 2*a(n-1) + (-1)^n*a(floor(n/2)); a(1)=1.at n=13A089067
- a(n) = 529*n^2 - 2*n.at n=4A158364
- Number of partitions of n containing at least one part m-10 if m is the largest part.at n=32A212550
- A010062(2^n-1).at n=11A228952
- T(n,k)=Number of (n+1)X(k+1) 0..2 arrays x(i,j) with row sums sum{x(i,j), j=1..k+1} nondecreasing, and column sums sum{i^2*x(i,j), i=1..n+1} nondecreasing.at n=28A233374
- Number of (1+1)X(n+1) 0..2 arrays x(i,j) with row sums sum{x(i,j), j=1..n+1} nondecreasing, and column sums sum{i^2*x(i,j), i=1..1+1} nondecreasing.at n=7A233375
- Number of 3-element subsets of {1,...,n} whose sum has more than 3 divisors.at n=47A241564
- Number T(n,k) of ways k L-tiles can be placed on an n X n square; triangle T(n,k), n>=0, 0<=k<=A229093(n), read by rows.at n=45A243608
- Number of ways three L-tiles can be placed on an n X n square.at n=8A243646
- Numbers k such that 7*R_(k+2) - 10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=4A257032
- a(n) = number of steps to reach 0 when starting from k = (n^3)-1 and repeatedly applying the map that replaces k with k - A055401(k), where A055401(k) = the number of positive cubes needed to sum to k using the greedy algorithm.at n=47A261228
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 251", based on the 5-celled von Neumann neighborhood.at n=26A271018
- Numbers n>1 such that the difference between log(n) and its best rational approximation as x/y with y<=n produces a new minimum of abs(log(n)-x/y). x/y is provided as A306976/A306977.at n=19A306975
- Numbers k such that 465*2^k+1 is prime.at n=29A318193
- a(n) = Sum_{k=1..n} phi(k) * (floor(n/k)^4 - floor((n-1)/k)^4).at n=14A344600