13656
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
- 2
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 34200
- Proper Divisor Sum (Aliquot Sum)
- 20544
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 4544
- Möbius Function
- 0
- Radical
- 3414
- Omega Function (Ω)
- 5
- 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
- 151
- 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
- Expansion of a modular function for Gamma_0(21).at n=21A002511
- Series for second perpendicular moment of square lattice (eventually changes sign).at n=11A006730
- a(n) = Sum_{i=0..floor(n/2)} T(2i,n-2i), array T as in A049735.at n=23A049738
- Sum of divisors of Woodall (or Riesel) numbers; sigma(A003261(n)); sigma(n*2^n - 1).at n=9A063515
- Numbers k such that iterating phi(sigma(k)-phi(k)) starting from k leads to the fixed point 8064.at n=32A077096
- a(n) = 8/3 - 5*(-2)^n/3.at n=13A083581
- Triangle read by rows: T(n,k) = number of permutations p of [n] such that max(|p(i)-i|)=k (n>=1, 0<=k<=n-1).at n=34A130152
- Number of permutations of floor(i*8/5), i=0..n-1, with all sums of two adjacent terms unique.at n=7A147889
- Numbers k such that both k and k^2 are sums of a twin prime pair.at n=8A213784
- Triangle T(n,k) in which n-th row lists in increasing order all positive integers with a representation as totally balanced 2n digit binary string without totally balanced proper prefixes such that all consecutive totally balanced substrings are in nondecreasing order; n>=1, 1<=k<=A000081(n).at n=38A216648
- Sum_{k, k|n} 2^(k-1) + Sum_{1<=k<=n, gcd(k,n)=1} 2^(k-1).at n=13A245392
- Number of solutions to c(1)*prime(3) + ... + c(2n-1)*prime(2n+1) = -1, where c(i) = +-1 for i > 1, c(1) = 1.at n=11A261063
- Least positive integer k such that both k and k*n belong to the set {m>0: 2*prime(prime(m))+1 = prime(p) for some prime p}.at n=46A261362
- Strings of 5 digits from 1...9, such that no formula using the single digits in the given order exists that evaluates to 0.at n=5A288355
- Numbers k such that (32*10^k - 77)/9 is prime.at n=17A290153
- Wiener index of the n X n king graph.at n=8A292053
- Number of permutations p of [n] such that max_{j=1..n} |p(j)-j| = 6.at n=2A323802
- Where 2^n appears in A340488 for the first time.at n=7A340498
- Numbers such that the two numbers before and the two numbers after are squarefree semiprimes.at n=28A358666
- Numbers k such that A003415(k) == A276085(k) (mod 5^5), where A003415 is the arithmetic derivative and A276085 is the primorial base log-function.at n=11A391865