2809
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 3
- Divisor Sum
- 2863
- Proper Divisor Sum (Aliquot Sum)
- 54
- 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
- 2756
- Möbius Function
- 0
- Radical
- 53
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 1
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- no
- Perfect Square
- yes
- 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
- 159
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- Squarefree Number
- no
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- yes
- Achilles Number
- no
- Perfect Power
- yes
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Squares of primes.at n=15A001248
- Genus of modular group Gamma(n) = genus of modular curve Chi(n).at n=43A001767
- Sum of squares of primes dividing n.at n=52A005063
- Sum of squares of odd primes dividing n.at n=52A005066
- Sum of squares of primes = 2 mod 3 dividing n.at n=52A005075
- Sum of squares of primes = 1 mod 4 dividing n.at n=52A005079
- Number of non-1-Hamiltonian simplicial polyhedra with n nodes.at n=12A007035
- Coordination sequence T2 for Zeolite Code MEL.at n=34A008151
- In the prime factorization of n, increment odd powers and decrement even powers (multiplicative and self-inverse).at n=52A011262
- exp(arcsin(x)-tan(x))=1-1/3!*x^3-7/5!*x^5+10/6!*x^6-47/7!*x^7...at n=9A013398
- arcsin(arcsin(x)-tan(x))=-1/3!*x^3-7/5!*x^5-47/7!*x^7+2809/9!*x^9...at n=3A013399
- Numbers that are not the sum of a square and a prime.at n=43A014090
- Odd squares: a(n) = (2n+1)^2. Also centered octagonal numbers.at n=26A016754
- a(n) = (3n+2)^2.at n=18A016790
- a(n) = (4*n + 1)^2.at n=13A016814
- a(n) = (5*n + 3)^2.at n=10A016886
- a(n) = (6*n + 5)^2.at n=8A016970
- a(n) = (7*n + 4)^2.at n=7A017030
- a(n) = (8*n + 5)^2.at n=6A017126
- a(n) = (9*n + 8)^2.at n=5A017258