9021
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 12544
- Proper Divisor Sum (Aliquot Sum)
- 3523
- 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
- 5760
- Möbius Function
- -1
- Radical
- 9021
- Omega Function (Ω)
- 3
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 140
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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) = (4*n+1)*(4*n+5).at n=23A003185
- Expansion of 1/((1-x)(1-4x)(1-8x)).at n=4A016224
- Numbers whose maximal base-9 run length is 4.at n=18A037999
- (s(n)+1)/10, where s(n)=n-th base 10 palindrome that starts with 9.at n=24A043088
- Numbers having four 3's in base 9.at n=1A043468
- Number of binary arrangements without adjacent 1's on n X n torus connected ne-sw n-s nw-se.at n=4A067959
- a(n) = (11*n^2 - 11*n + 2)/2.at n=40A069125
- A measure of how close r^n is to an integer where r is the real root of x^3-x-1, i.e.. r = (1/2 + sqrt(23/108))^(1/3) + (1/2 - sqrt(23/108))^(1/3) = 1.3247.... (Higher absolute value of a(n) means closer, negative means less than closest integer.)at n=55A084252
- Representative lunar primes.at n=27A088574
- Sum of largest parts (counted with multiplicity) of all partitions of n into odd parts.at n=34A092310
- Number of squares on infinite half chessboard at <=n knight moves from a fixed point on the diagonal.at n=36A098499
- Number of permutations of length n which avoid the patterns 321, 2143, 3124; or avoid the patterns 132, 2314, 4312, etc.at n=30A116731
- Start with 1013 and repeatedly reverse the digits and add 2 to get the next term.at n=8A120214
- Numbers k such that the numerator of the Bernoulli number B(2k) ends with the digits 691.at n=34A132184
- First trisection of A061037 (Balmer line series of the hydrogen atom).at n=31A142590
- a(n) = (8*n+5)*(8*n+9).at n=11A146302
- a(n) = 100*n^2 + 100*n + 21.at n=9A152161
- Diagonal sums of number triangle A113582.at n=23A154324
- Long legs of primitive Pythagorean triples (a,b,c) for which 2a+1, 2b+1 and 2c+1 are primes.at n=26A165237
- a(n) = 5*n^2 + 5*n - 9.at n=41A166150