2115
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
- 2
Divisibility
- Divisor Count
- 12
- Divisor Sum
- 3744
- Proper Divisor Sum (Aliquot Sum)
- 1629
- 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
- 1104
- Möbius Function
- 0
- Radical
- 705
- 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
- yes
- 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
- no
- Odd
- yes
Appears in sequences
- a(n) = 4*n^2 - 1.at n=23A000466
- a(n) = (4*n+1)*(4*n+3).at n=11A001539
- a(n) = -a(n-1) - 2*a(n-2).at n=24A001607
- a(n) = ceiling(n*phi^8), where phi is the golden ratio, A001622.at n=45A004963
- a(n) = n*(n+2) = (n+1)^2 - 1.at n=45A005563
- Oscillates under partition transform.at n=36A007210
- Coordination sequence T2 for Zeolite Code AFY.at n=38A008030
- Coordination sequence T1 for Zeolite Code ATT.at n=33A008041
- a(n) = floor( n*(n-1)*(n-2)*(n-3)/27 ).at n=17A011937
- Pseudoprimes to base 46.at n=30A020174
- a(n) = n*(13*n + 1)/2.at n=18A022271
- Place where n-th 1 occurs in A023131.at n=38A022793
- Convolution of A014306 (starting 0,0,1,1,0,1,1,1,1,...) and primes.at n=36A023674
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = A023532, t = A001950 (upper Wythoff sequence).at n=51A024374
- Every prefix prime in base 6 (written in base 6).at n=14A024766
- Every prefix and suffix prime in base 6 (written in base 6).at n=7A024774
- Every suffix prime and no 0 digits in base 6 (written in base 6).at n=26A024781
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = A023532, t = A001950 (upper Wythoff sequence).at n=50A025074
- Number of proper factorizations of the numbers with a record number of proper factorizations.at n=43A033834
- Positive numbers having the same set of digits in base 5 and base 8.at n=21A037431