2991
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
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 3992
- Proper Divisor Sum (Aliquot Sum)
- 1001
- 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
- 1992
- Möbius Function
- 1
- Radical
- 2991
- 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
- yes
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 48
- 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
- Coordination sequence T2 for Zeolite Code AFS.at n=42A008024
- Coordination sequence T2 for Zeolite Code TON.at n=34A008242
- Seven iterations of Reverse and Add are needed to reach a palindrome.at n=39A015986
- Cycle class sequence c(n) (the number of true cycles of length n in which a certain node is included) for zeolite BOG = Boggsite Na4Ca7[Al18Si78O192].74H2O starting with a T1 atom.at n=11A019083
- Numbers k such that the continued fraction for sqrt(k) has period 34.at n=32A020373
- Numbers k such that Fibonacci(k) == -2 (mod k).at n=45A023163
- a(n) = T(n,2n-5), T given by A027023.at n=7A027029
- 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 36.at n=15A031534
- Numbers n such that string 9,1 occurs in the base 10 representation of n but not of n-1.at n=32A044423
- Numbers m such that string 9,1 occurs in the base 10 representation of m but not of m+1.at n=32A044804
- Numbers whose base-4 representation contains exactly three 2's and three 3's.at n=4A045151
- a(0) = 0; for n >= 0, a(n+1) = a(n) + x where x is the smallest nonnegative number that is not equal to a(i) +- a(k) for any 0 <= i <= n, 0 <= k <= n.at n=46A047699
- Coordination sequence T5 for Zeolite Code DON.at n=37A047957
- a(n)=a(n-1)+a(m), where m=2n-2-2^(p+1) and 2^p<n-1<=2^(p+1), for n >= 4.at n=25A050067
- a(1) = 1, a(2) = 3; for n>2, a(n) = least value > a(n-1) such that pairwise differences are unique.at n=40A051788
- Number of primitive (period n) step cyclic shifted sequence structures using a maximum of six different symbols.at n=9A056443
- C(n+3)=2*C(n), where C(n) is Cototient(n) := n - phi(n) (A051953).at n=21A063480
- Numbers which need seven 'Reverse and Add' steps to reach a palindrome.at n=38A065212
- Numbers n such that phi(n) = reversal(n).at n=5A069215
- Numbers n such that reverse(n) = phi(n) (mod n).at n=9A072392