2826
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 6162
- Proper Divisor Sum (Aliquot Sum)
- 3336
- 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
- 936
- Möbius Function
- 0
- Radical
- 942
- Omega Function (Ω)
- 4
- 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
- 128
- 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
- Numbers k such that 9*2^k + 1 is prime.at n=26A002256
- Coefficients in expansion of permanent of infinite tridiagonal matrix shown below.at n=55A003113
- a(n) = 1 + n/2 + 9*n^2/2.at n=25A006137
- Number of loopless tree-rooted planar maps with 3 vertices and n faces and no isthmuses.at n=7A006428
- Coordination sequence T2 for Zeolite Code AST.at n=39A008037
- s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (Fibonacci numbers), t = A000201 (lower Wythoff sequence).at n=19A024464
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (Fibonacci numbers), t = A000201 (lower Wythoff sequence).at n=18A025084
- a(n) = (d(n)-r(n))/5, where d = A026049 and r is the periodic sequence with fundamental period (4,1,4,0,1).at n=30A026051
- Number of partitions of n with equal nonzero number of parts congruent to each of 0, 2 and 4 (mod 5).at n=46A035586
- Number of odd nonprimes <= (2n+1)^2.at n=43A038377
- Numbers k such that the string 8,0 occurs in the base 9 representation of k but not of k-1.at n=37A044323
- Numbers n such that string 2,6 occurs in the base 10 representation of n but not of n-1.at n=31A044358
- Numbers n such that string 8,0 occurs in the base 9 representation of n but not of n+1.at n=37A044704
- Numbers n such that string 2,6 occurs in the base 10 representation of n but not of n+1.at n=31A044739
- a(n) = Sum_{i=0..floor(n/2)} T(2i,n-2i) where T is A049615.at n=41A049618
- a(n) = Sum_{i=0..floor((n+1)/2)} T(2i+1,n-2i-1) where T is A049615.at n=41A049619
- a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049727.at n=30A049739
- a(n) = a(n-1) + a(m) for n >= 4, where m = 2^(p+1) + 2 - n and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = a(2) = 1 and a(3) = 2.at n=39A050029
- Numbers of the form (10*a + b)^2 + (10*b + a)^2 with a and b less than 10, in numerical order.at n=14A061191
- Multiples of 9 having only even digits.at n=22A061831