2109
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 3040
- Proper Divisor Sum (Aliquot Sum)
- 931
- 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
- 1296
- Möbius Function
- -1
- Radical
- 2109
- 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
- 81
- 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
- Square pyramidal numbers: a(n) = 0^2 + 1^2 + 2^2 + ... + n^2 = n*(n+1)*(2*n+1)/6.at n=18A000330
- Number of points of norm <= n in cubic lattice.at n=8A000605
- The coding-theoretic function A(n,4,4).at n=34A001843
- a(n) = binomial(n+3, 3)/4 for odd n, n*(n+2)*(n+4)/24 for even n.at n=35A006918
- Coordination sequence T3 for Zeolite Code DAC.at n=29A008069
- Molien series of 4-dimensional representation of cyclic group of order 4 over GF(2) (not Cohen-Macaulay).at n=35A008610
- Coordination sequence T3 for Zeolite Code -CHI.at n=29A009848
- a(n) = floor(n*(n-1)*(n-2)/24).at n=38A011842
- a(n) = floor( n*(n-1)*(n-2)/26 ).at n=39A011908
- Odd square pyramidal numbers.at n=9A015221
- Expansion of 1/Product_{m>=1} (1 - m*q^m)^19.at n=3A022743
- a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = floor(n/2), s = (odd natural numbers).at n=17A025112
- a(n) = T(2n,n+2), T given by A026736.at n=5A026851
- a(n) = T(2n+1,n+1), T given by A026736.at n=6A026854
- Coordination sequence T2 for Zeolite Code SAT.at n=33A027374
- Numbers k such that k*(k+7) is a palindrome.at n=8A028564
- a(n) = n^2 - 7.at n=43A028881
- Odd numbers to the right of the central elements of the (1,2)-Pascal triangle A029635.at n=42A029650
- Odd numbers to the left of the central elements of the (2,1)-Pascal triangle A029653.at n=43A029664
- Positions of record values in A030787.at n=43A030792