1639
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 19
- Digital Root
- 1
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 1800
- Proper Divisor Sum (Aliquot Sum)
- 161
- 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
- 1480
- Möbius Function
- 1
- Radical
- 1639
- 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
- 104
- 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
- 9-gonal (or enneagonal or nonagonal) numbers: a(n) = n*(7*n-5)/2.at n=22A001106
- Erroneous version of A002572.at n=15A001180
- Number of partitions of 1 into n powers of 1/2; or (according to one definition of "binary") the number of binary rooted trees.at n=15A002572
- Number of paraffins.at n=18A005998
- Number of unlabeled distributive lattices on n nodes.at n=16A006982
- Expansion of (1-x)/(1-2*x+x^2-2*x^3).at n=12A007909
- Coordination sequence T3 for Zeolite Code -CLO.at n=36A009852
- Odd numbers k such that phi(k) | sigma_3(k).at n=33A015809
- a(n) = n*(27*n + 1)/2.at n=11A022285
- Numbers k such that Fibonacci(k) == 89 (mod k).at n=25A023182
- a(n) = least m such that if r and s in {1/1, 1/2, 1/3, ..., 1/n} satisfy r < s, then r < k/m < (k+4)/m < s for some integer k.at n=18A024846
- Expansion of (1 -x -sqrt(1-2*x-11*x^2))/(6*x^2).at n=7A025237
- Index of 10^n within the sequence of the numbers of the form 5^i*10^j.at n=47A025743
- Sum of numbers between the two n's in A026272.at n=37A026275
- a(n) = n + (n+1)^2.at n=39A028387
- Numbers k such that k*(k + 9) is a palindrome.at n=9A028570
- Odd 9-gonal (or enneagonal) numbers.at n=11A028991
- Numbers having period-2 7-digitized sequences.at n=28A031202
- Lucky numbers with smallest increasing gaps (upper terms).at n=13A031885
- Shifts left 2 places under "EFK" (unordered, size, unlabeled) transform.at n=17A032307