17120
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 11
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 24
- Divisor Sum
- 40824
- Proper Divisor Sum (Aliquot Sum)
- 23704
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 6784
- Möbius Function
- 0
- Radical
- 1070
- Omega Function (Ω)
- 7
- 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
- yes
- 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
- 27
- 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
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (F(2), F(3), ...), t = (odd natural numbers).at n=23A024592
- a(n) = s(1)*t(n) + s(2)*t(n-1) + ... + s(k)*t(n-k+1), where k = [ n/2 ], s = (F(2), F(3), F(4), ...), t = (odd natural numbers).at n=22A025106
- 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 65.at n=33A031563
- Number of partitions of n into parts not of the form 15k, 15k+2 or 15k-2. Also number of partitions with 1 part of size 1 and differences between parts at distance 6 are greater than 1.at n=43A035956
- a(n) equals floor(Vc(n) - Vs(n)), where Vc(n) is the volume of the cube with side length n and Vs(n) is the volume of the sphere of diameter n.at n=32A057671
- Numbers k such that 2^k - 17 is prime.at n=35A059611
- Number of basis partitions of n+81 with Durfee square size 9.at n=24A069252
- Pentagonal numbers (A000326) whose digit reversal is a semiprime (A001358).at n=32A115709
- Pentagonal numbers with prime indices.at n=27A116995
- a(n) gives the number of nonisomorphic connected compact Lie groups of dimension n which are simple products.at n=54A177821
- Pentagonal numbers which are the arithmetic mean of two consecutive primes.at n=14A234531
- Number of irreducible polynomials occurring as the first component of a vertex in the Fibonacci zero tree, generated as in Comments.at n=22A262841
- Square array read by antidiagonals downwards: T(k,n) = sum of the site-perimeters of words of length n >= 1 over an alphabet of size k >= 1.at n=31A292767
- Pentagonal numbers divisible by 4.at n=27A298397
- a(n) = n^4/6 - 2*n^3/3 - n^2/6 + 5*n/3 + 1.at n=18A299198
- a(n) = (A001359(n+1)^2 - 1)/24, where A001359 = lesser of twin primes; or: pentagonal numbers (A000326) whose indices are twin ranks (A002822).at n=27A308344
- Composite numbers d such that the period k of the repetend of 1/d is > 1 and divides d-1, and d is the first such composite with a given period.at n=40A350220
- Pentagonal numbers that are abundant.at n=34A379264