9045
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 18
- Digital Root
- 9
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 16320
- Proper Divisor Sum (Aliquot Sum)
- 7275
- 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
- 4752
- Möbius Function
- 0
- Radical
- 1005
- Omega Function (Ω)
- 5
- 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
- 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
- no
- Narcissistic Number
- no
- Collatz Steps
- 21
- 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
- Number of inequivalent ways to color vertices of a regular tetrahedron using <= n colors.at n=18A006008
- a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (F(2), F(3), ...), t = (odd natural numbers).at n=20A024592
- a(n) = (2*n-1)*(4*n-1).at n=34A033567
- Triangular numbers that have some nontrivial permutation of digits which is also triangular.at n=35A034291
- Gaps of 10 in sequence A038593 (upper terms).at n=6A038660
- Numbers that are divisible by 5 and are the difference between two (different positive) cubes in at least one way.at n=39A038853
- Numbers ending with '5' that are the difference of two positive cubes.at n=27A038860
- 3 times pentagonal numbers: 3*n*(3*n-1)/2.at n=45A062741
- a(n) = smallest triangular number having no digit in common with the previous term, with a(1) = 1.at n=25A068818
- a(1) = 1; a(n) is the smallest triangular number > a(n-1) which differs from it at every digit.at n=27A068855
- Triangular numbers k*(k+1)/2 such that A068865(k) = k*(k+1)/2.at n=21A068866
- Triangular numbers containing 2k digits in which the sum of the first k digits = that of the rest.at n=8A068898
- Triangular numbers whose digit permutations yield at least two further triangular numbers.at n=8A069674
- Triangular numbers which are 5-almost primes.at n=26A076579
- Positive integers not expressible as the sum of a prime and a triangular number.at n=55A076768
- Rearrangement of triangular numbers such that the most significant digits follow the cyclic pattern 1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,...at n=44A077690
- Triangle read by rows in which the n-th row contains the n smallest triangular numbers with the least significant digits of the n-th triangular number.at n=38A095225
- The two digits touching the first comma have as absolute difference 0. The next such difference is 1. The next one is 2. Then 3, 4, 5... etc. When we reach 9 the differences start a new cycle: 0, 1, 2, 3... etc. Among many such possible sequences, this is the slowest increasing one starting with "1".at n=44A098795
- Numbers n such that n and its digit reversal R(n) both are difference of positive cubes.at n=15A109879
- Triangular numbers for which the sum of the digits is a heptagonal number.at n=14A117312