2119
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2296
- Proper Divisor Sum (Aliquot Sum)
- 177
- 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
- 1944
- Möbius Function
- 1
- Radical
- 2119
- Omega Function (Ω)
- 2
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 81
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- 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) = n*a(n-1) + (n-1)*a(n-2), a(0) = 1, a(1) = 1.at n=6A000255
- Triangle giving number L(n,k) of normalized k X n Latin rectangles.at n=29A001009
- Coefficients in expansion of permanent of infinite tridiagonal matrix shown below.at n=52A003113
- Numbers k where |cos(k)| (or |cosec(k)| or |cot(k)|) decreases monotonically to 0; also numbers k where |tan(k)| (or |sec(k)|, or |sin(k)|) increases.at n=11A004112
- Coordination sequence T2 for Zeolite Code ATT.at n=33A008042
- Coordination sequence T1 for Zeolite Code DFO.at n=35A009875
- Coordination sequence T6 for Zeolite Code DFO.at n=35A009880
- Triangle read by rows: T(n,k) is the number of permutations of [n] having k consecutive ascending pairs (0 <= k <= n-1).at n=27A010027
- Irregular triangle read by rows: T(n,k) (n>=1, 0 <= k <= floor(n/2)) = number of permutations of 1..n with exactly floor(n/2) - k runs of consecutive pairs up.at n=35A010029
- Irregular triangle read by rows: T(n,k) (n>=1, 0 <= k <= floor(n/2)) = number of permutations of 1..n with exactly floor(n/2) - k runs of consecutive pairs up.at n=18A010029
- a(n) = floor( n*(n-1)*(n-2)/22 ).at n=37A011904
- a(1) = 1; a(n+1) = floor((sum{k=1 to n} a(k)^3)^(1/3)).at n=41A016085
- Coordination sequence T3 for Zeolite Code TER.at n=31A016435
- Coordination sequence T2 for Zeolite Code SAO.at n=36A019572
- Numbers k such that the continued fraction for sqrt(k) has period 24.at n=36A020363
- a(n) = n*(25*n + 1)/2.at n=13A022283
- 6th differences of factorial numbers.at n=1A023043
- Least k such that tan(k) > tan(a(n-1)), for n >= 1, where a(0) = 0.at n=22A024814
- a(n) = T(2n, n-1), T given by A026758.at n=5A026760
- a(n) = Sum_{0<=j<=i<=n} A027170(i, j).at n=7A027180