17205
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
- 1
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 29184
- Proper Divisor Sum (Aliquot Sum)
- 11979
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8640
- Möbius Function
- 1
- Radical
- 17205
- Omega Function (Ω)
- 4
- 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
- yes
- 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
- 27
- Smith Number
- no
- 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
- no
- Odd
- yes
Appears in sequences
- a(n) = (n+1)*(n^2 +8*n +6)/6. Number of n-dimensional partitions of 4. Number of terms in 4th derivative of a function composed with itself n times.at n=44A008778
- a(1) = 3; a(n+1) = a(n)-th nonprime, where nonprimes begin at 0.at n=40A025000
- a(n) = 49*(n*(n+1)/2) + 6.at n=26A061792
- Ninth column of quadrinomial coefficients.at n=7A064055
- Triangular numbers with sum of digits = 15.at n=27A068130
- Triangular numbers whose digit permutations yield at least two further triangular numbers.at n=12A069674
- Terms of A073872 that do not change their position in the rearrangement; i.e., values of A073872(n) which equal n(n+1)/2.at n=13A073873
- Triangular numbers which are also happy numbers (cf. A007770).at n=28A076712
- a(1) = 1; for n > 1, a(n) = smallest triangular number which is n times another triangular number > 1, or -1 if no such number exists.at n=36A077672
- Expansion of (1-x)^(-1)/(1-2*x+2*x^2+x^3).at n=18A077861
- Number of binary necklaces of length n with no subsequence 000.at n=20A093305
- Hexagonal numbers for which the sum of the digits is also a hexagonal number.at n=19A117062
- Hexagonal numbers for which the product of the digits is also a hexagonal number.at n=39A117063
- Hexagonal numbers for which both the sum of the digits and the product of the digits are also hexagonal numbers.at n=10A117064
- Triangular numbers for which the sum of the digits is a hexagonal number.at n=38A117309
- Triangular numbers that can be written as sum of three positive cubes.at n=37A119977
- Triangular numbers t which are average of two consecutive primes p and p+4.at n=20A129752
- Triangular numbers which are the average of two consecutive primes.at n=40A130178
- a(n) = 5*n*(5*n + 1)/2.at n=37A144312
- 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=32A144524