1221
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 6
- Digital Root
- 6
- Palindromic Number
- yes
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 1824
- Proper Divisor Sum (Aliquot Sum)
- 603
- 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
- 720
- Möbius Function
- -1
- Radical
- 1221
- 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
- 39
- 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) = a(n-1) + a(n-2) - 1.at n=15A001588
- Number of multigraphs with 4 nodes and n edges.at n=17A003082
- a(n) = (4*n+1)*(4*n+5).at n=8A003185
- a(n) = floor(n*phi^8), where phi is the golden ratio, A001622.at n=26A004923
- a(n) = round(n*phi^8), where phi is the golden ratio, A001622.at n=26A004943
- a(n) = n*(5*n+1)/2.at n=22A005475
- Coefficient of x^4 in expansion of (1+x+x^2)^n.at n=10A005712
- a(n) = a(n-1) + a(n - 1 - number of even terms so far).at n=26A006336
- a(n) = Sum_{k=1..n-1} lcm(k,n-k).at n=22A006580
- Second (lower) diagonal of partition triangle A047812.at n=9A007045
- McKay-Thompson series of class 6c for Monster.at n=12A007262
- Integers written in factorial base.at n=41A007623
- Concatenation of sequence (1, 2, ..., floor((n-1)/2), floor(n/2), floor(n/2)-1, ..., 1) for n >= 1.at n=3A007907
- Numbers that contain only 1's and 2's. Nonempty binary strings of length n in lexicographic order.at n=20A007931
- Numbers that contain only 1's, 2's and 3's.at n=51A007932
- Poincaré series [or Poincare series] of Lie algebra associated with a certain braid group.at n=7A007993
- Coordination sequence T4 for Zeolite Code NON.at n=21A008215
- Degrees of irreducible representations of group U3(11).at n=16A008944
- Degrees of irreducible representations of group U3(11).at n=15A008944
- Degrees of irreducible representations of group U3(11).at n=14A008944