15126
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 30264
- Proper Divisor Sum (Aliquot Sum)
- 15138
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- yes
Derived Values
- Euler's Totient
- 5040
- Möbius Function
- -1
- Radical
- 15126
- 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
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 84
- Smith Number
- yes
- 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
- yes
- Odd
- no
Appears in sequences
- a(n) = a(n-1) + a(n-2) + 1, with a(0) = 0 and a(1) = 2.at n=19A001610
- a(n) = floor(n*phi^20), where phi is the golden ratio, A001622.at n=1A004935
- a(n) = F(2n+1) + F(2n-1) - 1.at n=10A005592
- Number of cyclic binary n-bit strings with no alternating substring of length > 2.at n=19A007039
- Number of (marked) cyclic n-bit binary strings containing no runs of length > 2.at n=19A007040
- a(n) = floor(phi^n), where phi = (1+sqrt(5))/2 is the golden ratio.at n=20A014217
- Triangle of rooted planar maps up to orientation-preserving isomorphisms.at n=52A046653
- Restricted partitions.at n=20A049284
- Numbers which are the sum of their proper divisors containing the digit 5.at n=19A059464
- Cyclotomic polynomials Phi_n at x=phi, ceiled up (where phi = tau = (sqrt(5)+1)/2).at n=19A063707
- Main diagonal of number array A082105.at n=11A082106
- Number of numbers k which give 1 after applying exactly n iterations of the 3k+1 algorithm (if a number is even, divide it by 2; if it is odd, multiply by 3 and add 1). This total includes numbers k which also give 1 for a smaller number of iterations (i.e., for this sequence we do not assume the algorithm halts when 1 is reached).at n=40A082538
- a(n) = Fibonacci(n-1) + Fibonacci(n+1) - (-1)^n.at n=20A098600
- Expansion of 1/(1-5*x+x^3).at n=6A099504
- Matrix cube of triangle A105535 and, in this flattened form as read by rows, also equals diagonal 2 of A105535.at n=58A105539
- a(n) = L(3*n)/L(n), where L(n) = Lucas number.at n=10A110391
- Merged values of A014217 = {floor(((1+sqrt(5))/2)^n)}, A000149 = {floor(e^n)}, and A001672 = {floor(Pi^n)}, with multiplicity.at n=39A119604
- Numbers that are the sum of exactly two sets of Fibonacci numbers.at n=34A122194
- a(n) = A014217(n+1) - A115360(n+2).at n=18A142584
- Semiperimeter of the n-th Heronian triangle.at n=7A151961