9805
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 22
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 12312
- Proper Divisor Sum (Aliquot Sum)
- 2507
- 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
- 7488
- Möbius Function
- -1
- Radical
- 9805
- 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
- 135
- 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
- Number of subsequences of [ 1,...,n ] in which each odd number has an even neighbor.at n=15A007455
- a(n) = 3*a(n-1) + 2*a(n-2), with a(0)=1, a(1)=5.at n=7A007483
- a(n) = (n+1)*(n^2 +8*n +6)/6. Number of n-dimensional partitions of 4. Number of terms in 4th derivative of a function composed with itself n times.at n=36A008778
- a(n) = floor( n*(n-1)*(n-2)/28 ).at n=66A011910
- Strong pseudoprimes to base 23.at n=14A020249
- a(n) = Sum_{k=floor((n+1)/2)..n} T(k,n-k); i.e., a(n) is n-th diagonal sum of left-justified array T given by A027011.at n=21A027022
- Sums of 7 distinct powers of 3.at n=30A038469
- Average of squares of successive primes: a(n) = (prime(n+1)^2 + prime(n)^2)/2, with n >= 2.at n=23A075892
- a(n) is the smallest m > 1 such that m divides Sum_{k=1..m} prime(k)^n.at n=41A085450
- Number of primes of the form 30k + 29 less than 10^n.at n=5A091172
- Positions of 9 in partition of decimal expansion of Pi A104807.at n=33A104809
- Start with 1 and repeatedly reverse the digits and add 52 to get the next term.at n=21A118149
- Start with 1027 and repeatedly reverse the digits and add 16 to get the next term.at n=66A119455
- Values of hypotenuse of primitive Pythagorean triples which can have four different shapes (that is, four different sets of "legs").at n=35A159781
- Appearance radii of visible vectors in the medial axis test mask for the Euclidean distance in Z^2.at n=14A171988
- Composite numbers of form 8n+5 with all prime factors of form 8m+5.at n=40A175486
- a(n) = n*(14*n + 13) + 3.at n=26A195029
- Numbers n such that n^2 is a concatenation of two nonzero squares with no trailing zeros in n.at n=44A198035
- Number of partitions of n such that the number of parts and the largest part and the smallest part are pairwise coprime.at n=35A201218
- Array: row n shows the coefficients of the characteristic polynomial of the n-th principal submatrix of (f(i,j)), where f(i,1)=f(1,j)=1, f(i,i)=2i-1; f(i,j)=0 otherwise; as in A204181.at n=31A204182