6686
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 26
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 10032
- Proper Divisor Sum (Aliquot Sum)
- 3346
- 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
- 3342
- Möbius Function
- 1
- Radical
- 6686
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- 44
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- 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
- yes
- Odd
- no
Appears in sequences
- Boustrophedon transform of Bell numbers.at n=7A000764
- a(n) = [ a(n-1)/a(1) + a(n-2)/a(2) + ... + a(1)/a(n-1) ], for n >= 3.at n=27A022869
- a(n) = Sum_{k=0..n} T(n,k), T given by A026725.at n=12A026732
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 80.at n=18A031578
- Number of partitions of n with equal nonzero number of parts congruent to each of 1, 2 and 3 (mod 5).at n=57A035588
- Numbers having three 6's in base 10.at n=28A043515
- Numbers whose base-9 representation has exactly 5 runs.at n=31A043634
- McKay-Thompson series of class 23A for Monster.at n=23A058570
- Trajectory of n under the Reverse and Add! operation carried out in base 3 (presumably) does not reach a palindrome and (presumably) does not join the trajectory of any term m < n.at n=17A077405
- a(1)=1; for n>=2, a(n)=sum(1<=i<=j<=n-1, gcd(a(i),a(j))).at n=12A099050
- Triangle T(n,m) = sum_{k=m..n} A001263(k,m).at n=50A104711
- Near-repdigit semiprimes with 6 as repeated digit.at n=17A105987
- Numbers m such that the permutation of the first m natural numbers R_m(n)=if(1<=n<m-pi(m), c(n), if(n=m, 1, prime(n-m-pi(m)+1))) is a cyclic permutation where c(k) is the k-th composite number(for each natural number k, c(k)=A002808(k)).at n=21A108517
- Semiprimes which are divisible by their multiplicative digital root.at n=41A118696
- Semiprimes that are semiprimes turned upside-down.at n=39A119738
- McKay-Thompson series of class 23A for the Monster group with a(0) = 1.at n=23A134781
- Number of n X n binary arrays symmetric under horizontal and vertical reflection with all ones connected only in a 1010-1111-1010 pattern in any orientation.at n=14A147438
- Number of cubic equations ax^3 + bx^2 + cx + d = 0 with integer coefficients |a|,|b|,|c|,|d| <= n, a <> 0, having three real roots, of which at least two are equal.at n=29A155192
- a(n) = (11*n^2 + 19*n + 10)/2.at n=34A160749
- A partial-sum Narayana product.at n=61A162717