17861
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 23
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 4
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18252
- Proper Divisor Sum (Aliquot Sum)
- 391
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 17472
- Möbius Function
- 1
- Radical
- 17861
- 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
- 48
- 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
- a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ... + a(n-1)*a(1) for n >= 5, with a(1) = 1, a(2) = a(3) = 0, a(4) = 1.at n=15A025276
- Number of partitions of n with equal number of parts congruent to each of 0 and 1 (mod 5).at n=50A035552
- Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 17.at n=23A051982
- Numbers n for which there are exactly seven k such that n = k + reverse(k).at n=37A072431
- a(n) = 15*n*(n+1) + 11.at n=34A132208
- Square array, read by antidiagonals, where row n equals the crystal ball sequence for the 2*n-dimensional lattice A_n x A_n.at n=39A143007
- Square array, read by antidiagonals, where row n equals the crystal ball sequence for the 2*n-dimensional lattice A_n x A_n.at n=41A143007
- Crystal ball sequence for the A3 x A3 lattice.at n=5A143009
- Crystal ball sequence for the A_5 x A_5 lattice.at n=3A143011
- Semiprimes p*q with p < q and 2^p (mod q) == 2^q (mod p).at n=23A179839
- Numbers k^2 + (k+1)^2 that can be expressed as a sum of two squares in exactly one other way.at n=41A239527
- Number of primitive Pythagorean triangles (x, y, z) with legs x < y < 10^n.at n=4A239581
- Decimal representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 966", based on the 5-celled von Neumann neighborhood.at n=14A284539
- Composite hypotenuses of primitive Pythagorean triangles (A120961) that are not circumdiameters of non-Pythagorean primitive Heronian triangles (A285579).at n=22A329148
- a(n) = A048673(n^2).at n=39A337336
- Denominator of (1+sigma(s)) / ((s+1)/2), where s is the square of n prime-shifted once (s = A003961(n)^2 = A003961(n^2)).at n=39A337339
- Number of vertices formed in a square by straight line segments when connecting the four corner vertices to the points dividing the sides into n equal parts.at n=32A355949
- Centered square numbers which are semiprime.at n=43A371016