16645
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 22
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 19980
- Proper Divisor Sum (Aliquot Sum)
- 3335
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 13312
- Möbius Function
- 1
- Radical
- 16645
- 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
- 66
- Smith Number
- yes
- 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
- Sums of 4 distinct powers of 4.at n=39A038472
- Numbers whose base-4 representation contains exactly four 0's and four 1's.at n=4A045037
- Average of squares of successive primes: a(n) = (prime(n+1)^2 + prime(n)^2)/2, with n >= 2.at n=29A075892
- Triangle read by rows of number of Catalan paths (nonnegative, starting and ending at 0, step +/-1) of 2n steps with all values less than or equal to k.at n=51A080935
- Number of Catalan paths (nonnegative, starting and ending at 0, step +-1) of 2*n steps with all values less than or equal to 7.at n=10A080938
- Indices of primes in sequence defined by A(0) = 79, A(k) = 10*A(k-1) - 81 for k > 0.at n=28A101130
- Number of perfect squared rectangles of order n up to symmetries of the rectangle and of its subrectangles if any.at n=15A110148
- Number of base 17 circular n-digit numbers with adjacent digits differing by 1 or less.at n=8A124710
- Triangle of numbers obtained from the partition array A134274.at n=31A134275
- Triangle of numbers obtained from the partition array A134274.at n=40A134275
- Numbers in A152022 which are not products of terms of A152021.at n=37A152023
- Let i be in {1,2,3,4} and let r >= 0 be an integer. Let p = {p_1, p_2, p_3, p_4} = {-3,0,1,2}, n=3*r+p_i, and define a(-3)=0. Then a(n)=a(3*r+p_i) gives the quantity of H_(9,2,0) tiles in a subdivided H_(9,i,r) tile after linear scaling by the factor Q^r, where Q=sqrt(2*cos(Pi/9)).at n=54A187496
- G.f.: exp( Sum_{n>=1} (x^n/n) * Product_{d|n} (1 + n*x^d/d) ).at n=25A205476
- Numbers n where tau(n) and n-tau(n) are perfect squares, with tau(n) the number of divisors of n (A000005).at n=32A245197
- The decimal values of binary sequences representing the "bits" form of adjacency matrices of non-isomorphic tournament graphs.at n=32A256373
- Triangle read by rows: number of generic n-rook placements with k rooks below the main diagonal.at n=11A269744
- Partial sums of repdigit numbers (A010785).at n=31A277209
- Numbers k such that (19*10^k + 191)/3 is prime.at n=20A280632
- Semiprimes A001358(k) = p*q such that p*q+p+q and r*s+r+s are consecutive primes, where A001358(k+1)=r*s.at n=8A330478
- Semiprimes of the form k^2 + 4.at n=27A360741