15685
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18828
- Proper Divisor Sum (Aliquot Sum)
- 3143
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 12544
- Möbius Function
- 1
- Radical
- 15685
- 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
- 53
- 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
- Pseudoprimes to base 56.at n=44A020184
- Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 11.at n=15A051976
- Number of 7 X 7 binary matrices with n ones, with no zero rows or columns, up to row and column permutation.at n=30A056079
- Numbers k that divide the sum of the partition numbers to k.at n=6A058856
- Third step in Goodstein sequences, i.e., g(5) if g(2)=n: write g(4)=A057650(n) in hereditary representation base 4, bump to base 5, then subtract 1 to produce g(5).at n=10A059934
- Start of the first run of exactly n consecutive odd composite numbers.at n=20A075067
- Numerator of Euler(n,3).at n=11A157805
- Eight bishops and one elephant on a 3 X 3 chessboard: a(n) = 2^(n+2)-3*F(n+1), with F(n) = A000045(n).at n=12A175661
- First string of 43 consecutive composite numbers.at n=1A177949
- The least semiprime (A001358) such that between it and the next n semiprimes, but not the next n+1 semiprimes, there are no primes.at n=12A228170
- a(n) is the smallest number k > 0 such that k, k + 1, ... , k + n - 1 are nonprime numbers, but k + n is prime.at n=42A230358
- Positions of records in A249431.at n=10A249432
- a(n) = G_n(12), where G is the Goodstein function defined in A266201.at n=3A271559
- a(n) is the smallest number k such that the difference between the next prime greater than k and k equals n.at n=41A309877
- G.f. A(x) satisfies: 1 = Sum_{n>=0} ( (1+x)^n - 11*x*A(x) )^n * 5^n / 6^(n+1).at n=2A323316
- a(n) = (3*n-1)*(n^4-18*n^3+179*n^2-582*n+720)/120.at n=16A381193