2106
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 9
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 20
- Divisor Sum
- 5082
- Proper Divisor Sum (Aliquot Sum)
- 2976
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 648
- Möbius Function
- 0
- Radical
- 78
- Omega Function (Ω)
- 6
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 81
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- yes
- Odd
- no
Appears in sequences
- Number of bipartite partitions of n white objects and 2 black ones.at n=15A000291
- E-trees with at most 3 colors.at n=5A007142
- Coordination sequence T3 for Zeolite Code BRE.at n=30A008060
- Number of ordered triples of integers from [ 1..n ] with no global factor.at n=23A015631
- a(n) = n*(25*n - 1)/2.at n=13A022282
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k=[ (n+1)/2 ], s = (natural numbers >= 2), t = (natural numbers >= 3).at n=25A024306
- a(n) = 2*(n+1) + 3*n + ... + (k+1)*(n+2-k), where k = floor(n/2).at n=25A024868
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = floor( n/2 ), s = natural numbers >= 2, t = natural numbers >= 3.at n=24A024869
- Coordination sequence T1 for Zeolite Code SAT.at n=33A027373
- Numbers k such that k^2+k+2 is a palindrome.at n=19A027712
- Expansion of (theta_3(z)*theta_3(11z) + theta_2(z)*theta_2(11z))^3.at n=25A028611
- 6 times triangular numbers: a(n) = 3*n*(n+1).at n=26A028896
- Numbers with 20 divisors.at n=28A030638
- Number of partitions in parts not of the form 7k, 7k+1 or 7k-1. Also number of partitions with no part of size 1 and differences between parts at distance 2 are greater than 1.at n=44A035937
- Composites n such that A001414(n) is odd and divides n.at n=19A036346
- Numbers whose base-7 representation contains exactly three 6's.at n=6A043419
- Numbers k such that string 6,6 occurs in the base 7 representation of k but not of k-1.at n=42A044186
- Numbers k such that string 7,2 occurs in the base 8 representation of k but not of k-1.at n=36A044245
- Numbers k such that string 0,0 occurs in the base 9 representation of k but not of k-1.at n=25A044251
- Numbers k such that the string 2,8 occurs in the base 9 representation of k but not of k-1.at n=29A044277