17766
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 27
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 5
Divisibility
- Divisor Count
- 32
- Divisor Sum
- 46080
- Proper Divisor Sum (Aliquot Sum)
- 28314
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 4968
- Möbius Function
- 0
- Radical
- 1974
- Omega Function (Ω)
- 6
- Little Omega Function (ω)
- 4
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- yes
- 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
- 185
- 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
- a(1) = 1, a(2) = 0; for n > 2, a(n) = n*Fibonacci(n-2) (with the convention Fibonacci(0)=0, Fibonacci(1)=1).at n=17A006490
- Fibonacci sequence beginning 0, 18.at n=16A022352
- Number of different ways to divide an n X n square into sub-squares, considering only the list of parts.at n=13A034295
- Triangular numbers that remain triangular when the least significant digit is moved to the beginning.at n=13A068071
- Smallest triangular number which is a multiple (>1) of the n-th triangular number.at n=26A068084
- Triangular numbers of the form 21*k.at n=35A069499
- Products of members of pairs in A075333.at n=32A075337
- Triangular numbers which are 6-almost primes.at n=13A076580
- Numbers k such that (10^k + 2)/6 is prime.at n=26A076850
- a(n) = (25*n^2 - 15*n + 2)/2.at n=38A080857
- Triangular numbers whose sum of squared digits is also triangular.at n=14A094890
- Expansion of 1/((x-1)*(x+1)*(x^2+x+1)*(x^2+x-1)*(x^2-x+1)*(x^2+1)*(x^4-x^2+1)).at n=21A109609
- Triangular numbers for which the sum of the digits equals the sum of the digits of the next triangular number.at n=10A117511
- Triangular numbers for which the sum of the digits is a cube.at n=7A117803
- Triangular numbers composed of digits {1,6,7}.at n=7A119140
- a(0)=1, a(1)=1; for n>1, a(n) = the sum of the two largest earlier terms which are both coprime to n.at n=55A122456
- Partial sum of centered tetrahedral numbers A005894.at n=17A132366
- G.f. satisfies: A(x) = 1 + x*A(x)/A(-x) + x^2*A(x)^2/A(-x)^2.at n=11A143560
- Triangular numbers n*(n+1)/2 with n composite, where number of prime factors of n, counted with multiplicity, is less than the number of prime factors in n+1.at n=34A144524
- Triangular numbers t such that all the digits needed to write the consecutive triangular numbers from 0 to t fill exactly an equilateral triangle (no holes, no overlaps).at n=15A158030