9810
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
- 1
Divisibility
- Divisor Count
- 24
- Divisor Sum
- 25740
- Proper Divisor Sum (Aliquot Sum)
- 15930
- 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
- 3270
- Omega Function (Ω)
- 5
- 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
- 166
- 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
- Start with 1, apply 1->12, 21->21, 22->21, 2->2 (for final 2); a(n) = length of n-th term.at n=28A013950
- Arrange digits of squares in descending order.at n=33A028908
- Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 22.at n=8A031700
- Expansion of (1 + x)*(1 - x + x^2)/((1 - x)^4*(1 + x + x^2)).at n=43A070333
- Number of primes of the form 30k + 11 less than 10^n.at n=5A091167
- Numbers k such that k*((2^61-1)^2) - 1 and k*((2^61-1)^2) + 1 are twin primes.at n=4A099229
- a(n) = 81*n^2 + 9.at n=10A157888
- a(n) = 121*n^2 + n.at n=8A173267
- The consecutive squares of numbers multiplied by their next consecutive integer.at n=15A193608
- Coefficients of a generalized Jaco-Lucas polynomial (odd indices) read by rows.at n=30A200073
- Number of 4-cycles in the Lucas cube Lambda(n).at n=15A245961
- Triangular array: row n gives the coefficients of the polynomial p(n,x) defined in Comments.at n=49A247376
- Number of length-4 0..n arrays with no repeated value equal to the previous repeated value.at n=8A269468
- a(n) = (27*3^n - 63)/2.at n=5A277105
- Number of nX4 0..1 arrays with every element unequal to 1, 2, 4, 5 or 6 king-move adjacent elements, with upper left element zero.at n=7A304700
- T(n,k)=Number of nXk 0..1 arrays with every element unequal to 1, 2, 4, 5 or 6 king-move adjacent elements, with upper left element zero.at n=58A304704
- Expansion of Product_{k>0} (1 + k*(k+1)/2 * x^(k*(k+1)/2)).at n=47A319256
- Number of n-digit base-10 palindromes (A002113) that cannot be written as the sum of two positive base-10 palindromes.at n=8A319586
- a(n) is the number of 2-point antichains in the poset D_{2n+1} of type D, whose elements are compositions of 2n+1.at n=17A344791
- a(n) is n in binary rendered as a base-10 number minus n in ternary rendered as a base-10 number.at n=17A347111