7509
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 10016
- Proper Divisor Sum (Aliquot Sum)
- 2507
- 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
- 5004
- Möbius Function
- 1
- Radical
- 7509
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- 26
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- 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
- Number of partitions of n into Fibonacci parts (with 2 types of 1).at n=35A007000
- Numbers k such that the continued fraction for sqrt(k) has period 62.at n=33A020401
- s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (Fibonacci numbers), t = A001950 (upper Wythoff sequence).at n=20A024465
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 56.at n=41A031554
- Numbers k such that the decimal part of k^(1/6) starts with a 'nine digits' anagram.at n=3A034281
- Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 22.at n=31A051963
- Expansion of (1+x-x^3)/((1-2*x)*(1-x^2)).at n=12A052997
- Integers n > 7059 such that the 'Reverse and Add!' trajectory of n joins the trajectory of 7059.at n=4A063058
- Numbers n for which one step of the Collatz iteration (3n+1)/2^r gives rise to values 41,35,29,23,17,11, and 5 for r=1,3,5,..,13.at n=5A072252
- a(n) = 4*a(n-1) + 1, a(1)=7.at n=5A072261
- Values of k such that {P(k), P(k+1), ..., P(k+7)} are all prime numbers, where P(k) = 4*k^2 - 154*k + 1523.at n=37A090110
- Values of k such that {P(k), P(k+1), ..., P(k+6)} are all prime numbers, where P(k) = 4*k^2 - 154*k + 1523.at n=48A090111
- Array read by antidiagonals. Rows contain odd numbers reaching same odd successor in Collatz function iteration.at n=30A099730
- a(n) = Sum_{i=1..n} (n-i+1)*phi(i).at n=41A103116
- The number of pairs of independent outcomes when rolling an n-sided die. Or in other words, the number of pairs of proper subsets A,B of a set S, such that #A/#S * #B/#S = #(A \intersect B)/#S.at n=7A158345
- Numbers k such that (k^3 + 2, n^3 + 4) is a twin prime pair.at n=43A178337
- Array T(n,k) of odd Collatz preimages read by antidiagonals.at n=41A178415
- Odd numbers producing 6 odd numbers in the Collatz iteration.at n=41A198589
- Rectangular array with all start numbers Mo(n, k), k >= 1, for the Collatz operation ud^(2*n-1), n >= 1, ending in an odd number, read by antidiagonals.at n=26A238476
- Number of inequivalent (mod D_4) ways four checkers can be placed on an n X n board.at n=4A242279