9990
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 27
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 32
- Divisor Sum
- 27360
- Proper Divisor Sum (Aliquot Sum)
- 17370
- 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
- 2592
- Möbius Function
- 0
- Radical
- 1110
- Omega Function (Ω)
- 6
- Little Omega Function (ω)
- 4
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
- Bessel polynomial {y_n}'(1).at n=5A001514
- [ exp(13/19)*n! ].at n=6A030865
- Sort then Add, a(1) =9.at n=13A033896
- Sort then Add, a(1)=27.at n=11A033903
- Numbers having three 9's in base 10.at n=27A043527
- Numbers n such that 101*2^n-1 is prime.at n=8A050576
- a(n) = n^4 - n.at n=10A058895
- Smallest multiple k*n of n which is a palindrome or becomes a palindrome when 0's are added on the left (e.g. 10 becomes 010 which is a palindrome).at n=54A062279
- Product of two triangular matrices C*S2.at n=18A064308
- Numbers k such that tau_3(k) (the number of ordered factorizations of k as k = r*s*t) divides k.at n=42A069147
- (Sum of digits of n)^4 - (sum of digits of n^4).at n=19A069978
- Numbers k such that iterating phi(sigma(k)-phi(k)) starting from k leads to the fixed point 8064.at n=4A077096
- a(n)^2 + 1 is largest prime of the form x^2 + 1 <= 10^n.at n=7A083845
- Numbers which are either a divisor or a multiple of their 9's complement.at n=33A084020
- Numbers k such that (k-1)*binomial(2k,k) + 1 is prime.at n=46A085793
- G.f.: Product((1+x^i)/(1-x^i),i=1..n-1)/(1-x^n), with n = 5.at n=34A091773
- Numbers whose set of base 10 digits is {0,9}.at n=14A097256
- A sequence derived from a Ferrers graph partition of 16.at n=7A098347
- {a(n)} is monotone increasing, with a(1)=1, a(2)=3 and, for n>2, a(n) is the smallest integer such that a(n) mod a(j) is never a(i) for any pair i,j with 1<=i<j<n.at n=47A100812
- Numbers which are the sum of two positive cubes and divisible by 37.at n=10A102618