6905
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8292
- Proper Divisor Sum (Aliquot Sum)
- 1387
- 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
- 5520
- Möbius Function
- 1
- Radical
- 6905
- 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
- 119
- 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
- no
- Odd
- yes
Appears in sequences
- Number of partitions of at most n into at most 5 parts.at n=32A002622
- Generalized Catalan numbers A(x)^2 -(1+x)^2*A(x) +x*(2+x+x^2) =0.at n=11A025242
- Numbers k such that 95*2^k+1 is prime.at n=26A032397
- Decimal part of a(n)^(1/5) starts with a 'nine digits' anagram.at n=3A034280
- Number of partitions of n into parts 3k or 3k+2.at n=53A035361
- Number of partitions satisfying cn(0,5) <= cn(1,5) and cn(0,5) <= cn(4,5).at n=33A039837
- a(n) = a(n-1) + a(m) for n >= 4, where m = 2^(p+1) + 2 - n and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1 and a(2) = a(3) = 3.at n=42A050065
- Let p(k) denote k-th prime; consider solutions (n,m) of the Diophantine system {p(p(n)+1)-p(p(n))=2, p(p(n))-6.p(p(m))=-1} (*); sequence gives values of m.at n=22A065511
- Expansion of (1 + x^2 - sqrt( 1 - 4*x + 2*x^2 + x^4)) / (2*x) in powers of x.at n=11A082582
- Number of Dyck paths of semilength n with no DDUU.at n=10A086581
- a(n) = smallest m >= 1 such that Sum_{k=1..m} log(k)/k >= n.at n=39A092753
- Number of compositions of n with first part 1 and no equal adjacent parts; this is column 1 of the array in A096568.at n=18A096569
- Triangle read by rows: T(n,k) is number of Dyck n-paths with k UUDDs, 0 <= k <= n/2.at n=36A098978
- Numbers k such that the k-th semiprime == 9 (mod k).at n=8A106134
- Triangle read by rows: T(n,k) is the number of Dyck paths of semilength n and having k DDUU's, where U=(1,1), D=(1,-1) (0<=k<=floor(n/2)-1 for n>=2).at n=22A114492
- Number of n X n binary arrays with all ones connected only in a 1000-1000-1111-0001 pattern in any orientation.at n=7A147269
- Number of n X n binary arrays with all ones connected only in a 1010-1111-1010 pattern in any orientation.at n=7A147436
- G.f.: (1+62*x+570*x^2+1095*x^3+530*x^4+57*x^5+x^6)/(1-x)^7.at n=3A160831
- 5 times centered pentagonal numbers: 5*(5*n^2 + 5*n + 2)/2.at n=23A164015
- Self-convolution of A180711.at n=28A180712