2665
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
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 3528
- Proper Divisor Sum (Aliquot Sum)
- 863
- 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
- 1920
- Möbius Function
- -1
- Radical
- 2665
- 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
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 53
- 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
- Generating function = Product_{m>=1} 1/(1 - x^m)^2; a(n) = number of partitions of n into parts of 2 kinds.at n=14A000712
- Centered square numbers: a(n) = 2*n*(n+1)+1. Sums of two consecutive squares. Also, consider all Pythagorean triples (X, Y, Z=Y+1) ordered by increasing Z; then sequence gives Z values.at n=36A001844
- Expansion of (psi(-x) / phi(-x))^5 in powers of x where phi(), psi() are Ramanujan theta functions.at n=7A001939
- Number of Dyck paths of knight moves.at n=12A005222
- Related to n-th powers of polynomials: factors complementary to A005730.at n=41A005731
- Pseudoprimes to base 3.at n=11A005935
- Coordination sequence T3 for Zeolite Code AEI.at n=39A008003
- Coordination sequence T1 for Zeolite Code RUT.at n=34A009897
- a(n) = floor(n*(n-1)*(n-2)/24).at n=41A011842
- Orders of cyclotomic polynomials containing a coefficient the absolute value of which is >= 3.at n=32A013591
- Sum of gcd(x, y) for 1 <= x, y <= n.at n=32A018806
- Number of squares on infinite chessboard at <= n knight's moves from a fixed square.at n=14A018836
- Pseudoprimes to base 9.at n=26A020138
- Pseudoprimes to base 14.at n=17A020142
- Pseudoprimes to base 27.at n=22A020155
- Pseudoprimes to base 32.at n=32A020160
- Pseudoprimes to base 38.at n=23A020166
- Pseudoprimes to base 42.at n=16A020170
- Pseudoprimes to base 44.at n=27A020172
- Pseudoprimes to base 68.at n=40A020196