8721
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 14400
- Proper Divisor Sum (Aliquot Sum)
- 5679
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 5184
- Möbius Function
- 0
- Radical
- 969
- Omega Function (Ω)
- 5
- 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
- 47
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- 4-dimensional pyramidal numbers: a(n) = n^2*(n^2-1)/12.at n=18A002415
- Geometric mean of phi(n) and sigma(n) is an integer, n odd.at n=22A015705
- a(n) = n*(n^2 + 12*n - 25)/6.at n=34A026057
- Odd numbers to the right of the central elements of the (1,2)-Pascal triangle A029635.at n=41A029650
- Odd numbers to the left of the central elements of the (2,1)-Pascal triangle A029653.at n=44A029664
- Arrange digits of cubes in descending order.at n=12A032554
- Numbers whose set of base-16 digits is {1,2}.at n=26A032936
- Every run of digits of n in base 16 has length 2.at n=31A033014
- Base-8 digits are, in order, the first n terms of the periodic sequence with initial period 2,1,0.at n=4A037525
- Denominators of continued fraction convergents to sqrt(6).at n=8A041007
- Denominators of continued fraction convergents to sqrt(24).at n=8A041039
- Positive integers having more base-16 runs of even length than odd.at n=32A044842
- Maximal elements of pairs of "Super Unitary Amicable Numbers", sorted by their minimal elements.at n=24A045614
- Numbers k > 1 such that, in base 4, k and k^2 contain the same digits in the same proportion.at n=29A061658
- Numerators of coefficients in series expansion of -512*(1+x)^3/(x-8)^3.at n=15A066414
- a(n) = 3^n mod n^3.at n=21A066607
- Numbers k such that phi(k) and sigma(k) are both perfect squares.at n=8A067781
- a(n) = 10*a(n-1) - a(n-2) for n > 1, a(0) = a(1) = 1.at n=5A072256
- a(n)*a(n+3) - a(n+1)*a(n+2) = 4, given a(0)=a(1)=1, a(2)=5.at n=9A080872
- An interleaved sequence of pyramidal and polygonal numbers.at n=34A081283