6651
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
- 6
- Divisor Sum
- 9620
- Proper Divisor Sum (Aliquot Sum)
- 2969
- 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
- 4428
- Möbius Function
- 0
- Radical
- 2217
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 2
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
- 44
- 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
- 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 81.at n=7A031579
- Sums of distinct powers of 9.at n=22A033046
- Base 9 digits are, in order, the first n terms of the periodic sequence with initial period 1,0,1.at n=4A033127
- Positive numbers having the same set of digits in base 2 and base 9.at n=18A037414
- Sums of 3 distinct powers of 9.at n=6A038488
- Numbers having three 1's in base 9.at n=34A043459
- a(1) = 9; a(n) is smallest number >= a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.at n=40A046259
- a(n) is the index of the smallest triangular number containing exactly n 2's.at n=4A048357
- Positive numbers whose product of digits is 10 times their sum.at n=38A062043
- G.f.: (1-x+2*x^2+2*x^3+2*x^4-x^5+x^6)/((1-x)*(1-x^2)^2*(1-x^3)).at n=42A083709
- Shadow of sqrt(2).at n=37A110557
- a(n) = ceiling(x(n)), where x(n) = 3*x(n-1)/2 and x(1) = 1.at n=20A117590
- Numbers k such that the k-th triangular number contains only digits {1,2,6}.at n=12A119104
- a(n) = round(2*(3/2)^n), using round-to-even method.at n=19A147789
- a(n+1)-+a(n)=prime, a(n+1)*a(n)=Average of twin prime pairs, a(1)=3,a(2)=10.at n=12A154496
- a(n) = n*(2*n^2 + 5*n + 1)/2.at n=17A162254
- a(n) = 5*n^2 + 5*n - 9.at n=35A166150
- The initial decimal digits of 2^a(n) are the decimal digits of n followed by n.at n=13A171652
- Self-convolution cube of A073711.at n=20A194279
- Vertex number of a square spiral in which the length of the first two edges are the legs of the primitive Pythagorean triple [21, 20, 29]. The edges of the spiral have length A195033.at n=35A195034