9920
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 28
- Divisor Sum
- 24384
- Proper Divisor Sum (Aliquot Sum)
- 14464
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 3840
- Möbius Function
- 0
- Radical
- 310
- Omega Function (Ω)
- 8
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 91
- 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
- yes
- Odd
- no
Appears in sequences
- Cake numbers: maximal number of pieces resulting from n planar cuts through a cube (or cake): C(n+1,3) + n + 1.at n=39A000125
- a(n) = 2*binomial(n,3).at n=32A007290
- Expansion of e.g.f. sinh(tan(x))*exp(x).at n=8A009605
- Expansion of sinh(x)*exp(tan(x)).at n=8A009624
- Number of nonisomorphic and nonantiisomorphic reflexive transitive and cotransitive (complement is transitive) relations.at n=12A030270
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 49.at n=29A031547
- Mean divisor of n differs by <= 1 from mean divisor of all numbers from 1 to n-1.at n=19A049010
- Truncated triangular pyramid numbers: a(n) = Sum_{k=9..n} (k*(k+1)/2 - 45).at n=31A051943
- Treated as strings, n begins with Floor(sqrt(n)).at n=43A069086
- Numbers in A070938 that set a new record for digital sums and ending digits.at n=13A070594
- a(n) is the smallest multiple of n such that a(n) mod 100 = n and S(n)=n where S(n) is the sum of the base-ten digits of n, or 0 if no such a(n) exists.at n=19A075154
- Consider iteration of the function f(x) = sigma(phi(x)) = A062402(x). Sequence lists the numbers k such that the trajectory of k returns to k.at n=30A096998
- a(n) = (4*n^3 + 6*n^2 + 8*n + 6)/3.at n=19A100504
- Numbers which are the sum of three positive cubes and divisible by 31.at n=42A104054
- Triangle, read by rows, where T(0,0) = 1, T(n,k) = 2^n*T(n-1,k) + T(n-1,k-1).at n=17A108084
- Triangle, read by rows, where T(0,0) = 1, T(n,k) = 2^n*T(n-1,k) - T(n-1,k-1).at n=17A108085
- An Euler triangle.at n=17A117414
- E.g.f. (x*tan(x)-x^2)/8 (even powers only).at n=5A117415
- Terms of A068563 that are not terms of A124240.at n=40A124241
- Triangle read by rows: T(n,k) is the number of partitions of the set {1,2,...,n} having exactly k blocks that contain both odd and even entries (0<=k<=floor(n/2)).at n=27A124418