17221
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18252
- Proper Divisor Sum (Aliquot Sum)
- 1031
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 16192
- Möbius Function
- 1
- Radical
- 17221
- 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
- 79
- 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
- Convolution of natural numbers with (1, p(1), p(2), ... ), where p(k) is the k-th prime.at n=31A023538
- Least m such that if r and s in {1/1, 1/3, 1/6,..., 1/C(n+1,2)} satisfy r < s, then r < k/m < s for some integer k.at n=44A024826
- Number of n-move king paths on 8 X 8 board from given corner to adjacent corner.at n=9A025598
- Centered 20-gonal (or icosagonal) numbers.at n=41A069133
- Centered 21-gonal numbers.at n=40A069178
- Expansion of g.f. (1+4*x)/((1-x)*(1+x)*(1-3*x)).at n=8A085287
- Number of partitions of n^2 into squares not less than n.at n=40A093116
- Numbers n such that 4*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=10A102982
- Numbers k such that the sum of the digits of (k^k - k!) is divisible by k.at n=21A109662
- Expansion of (1 +4*x -x^2)/((1-x^2)*(1-2*x-x^2)); a Pellian-related sequence.at n=10A114689
- Number of slanted 2 X n (i=1..2) X (j=i..n+i-1) 1..4 arrays with all 1s connected, all 2s connected, all 3s connected, all 4s connected, 1 in the upper left corner, 2 in the upper right corner, 3 in the lower left corner, 4 in the lower right corner, and with no element having more than 3 neighbors with the same value.at n=14A165394
- The number of reversible primes (palindromic or emirps) by increasing permissible leading digit and by length.at n=26A220344
- Values of n such that L(14) and N(14) are both prime, where L(k) = (n^2+n+1)*2^(2*k) + (2*n+1)*2^k + 1, N(k) = (n^2+n+1)*2^k + n.at n=42A227517
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 813", based on the 5-celled von Neumann neighborhood.at n=23A273640
- Number of nX4 0..1 arrays with every element unequal to 0, 1, 3, 4 or 6 king-move adjacent elements, with upper left element zero.at n=9A304540
- Numbers k such that 323*2^k+1 is prime.at n=11A322954
- Sequence a(n) = 3*A002559(n) - 2 determining the principal reduced indefinite binary quadratic form [1, a(n), -a(n)] for Markoff triples.at n=17A324250
- Number of free polyominoes with n cells with at most 4 collinear cell centers on any line in the plane.at n=11A380990