15985
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 28
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 20160
- Proper Divisor Sum (Aliquot Sum)
- 4175
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 12144
- Möbius Function
- -1
- Radical
- 15985
- 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
- 53
- 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 squares on infinite chessboard at <= n knight's moves from a fixed square.at n=34A018836
- Number of partitions of n with equal nonzero number of parts congruent to each of 0 and 2 (mod 5).at n=48A035563
- Numbers k such that k^2 contains only digits {0,2,5}, not ending with zero.at n=10A058425
- Centered 24-gonal numbers.at n=36A069190
- Numbers k such that k divides the numerator of B(2k) (the Bernoulli numbers), but gcd(3k, 8^k+1) > 3.at n=35A070192
- a(n) = (n-1)*(n-2)^3 - A003878(n-3), with a(1) = a(2) = 0 and a(3) = 2.at n=29A075681
- a(n) = 5*a(n-1) - a(n-2) + 1 with a(0)=1, a(1)=6.at n=6A089817
- Numbers n such that 6n+5, 6n+11, 6n+17, 6n+23 are consecutive primes or 6n+1, 6n+7, 6n+13, 6n+19 are consecutive primes.at n=36A090833
- Numbers k such that 6*k+1, 6*k+7, 6*k+13, 6*k+19 are consecutive primes.at n=17A090839
- Row sums of triangle A131252.at n=15A131253
- a(n) = 3*a(n-1) + A001651(n+1).at n=8A141397
- Alternate partial sums of the binomial coefficients binomial(3*n,n).at n=6A188676
- Number of length 5 nonnegative integer arrays starting and ending with 0 with adjacent elements unequal but differing by no more than n.at n=22A205342
- G.f. A(x) satisfies A(x) = Sum_{n>=0} x^(n^2) * A(x)^(2*n) / Product_{k=1..n} (1 - x^k*A(x))^2.at n=7A206639
- Numbers whose base-3 representation is a square when read in base 10.at n=24A267763
- Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).at n=33A286359
- Duplicate of A090839.at n=17A296055
- Number of integer partitions of n with a unique non-co-mode.at n=45A363129
- Expansion of e.g.f. exp( Sum_{k>=1} (2*k)! * (x/2)^k/k ).at n=4A370084