3991
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 22
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 4312
- Proper Divisor Sum (Aliquot Sum)
- 321
- 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
- 3672
- Möbius Function
- 1
- Radical
- 3991
- 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
- 51
- 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
- Related to cumulative height of rooted plane trees.at n=7A000758
- Number of sublattices of index n in generic 3-dimensional lattice.at n=50A001001
- Number of labeled graded partially ordered sets with n elements.at n=5A001833
- a(n) = floor( n*(n-1)*(n-2)/26 ).at n=48A011908
- Triangle of numbers associated with Genocchi numbers.at n=27A014780
- Triangle of numbers associated with Genocchi numbers.at n=33A014780
- Triangle of numbers associated with Genocchi numbers.at n=19A014782
- Triangle of numbers associated with Genocchi numbers.at n=25A014782
- Eight iterations of Reverse and Add are needed to reach a palindrome.at n=14A015988
- Pseudoprimes to base 17.at n=16A020145
- Numbers k such that the continued fraction for sqrt(k) has period 68.at n=5A020407
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 26 ones.at n=34A031794
- Number of partitions of n with equal number of parts congruent to each of 1 and 4 (mod 5).at n=40A035558
- Numbers m such that string 9,1 occurs in the base 10 representation of m but not of m+1.at n=43A044804
- a(n) = T(2n-1,n), array T given by A048225.at n=33A048234
- a(n) = least value such that sequence increases and pairwise differences are unique.at n=46A058335
- McKay-Thompson series of class 24B for Monster.at n=22A058572
- Numbers k such that phi(sigma(k^3)) is a square.at n=47A063796
- Semiprimes p1*p2 such that p2 > p1 and p2 mod p1 = 8.at n=23A064906
- Numbers which need eight 'Reverse and Add' steps to reach a palindrome.at n=10A065213