4991
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 23
- Digital Root
- 5
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 6144
- Proper Divisor Sum (Aliquot Sum)
- 1153
- 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
- 3960
- Möbius Function
- -1
- Radical
- 4991
- Omega Function (Ω)
- 3
- 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
- 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
- yes
- Narcissistic Number
- no
- Collatz Steps
- 72
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- Centered octahedral numbers (crystal ball sequence for cubic lattice).at n=15A001845
- a(n) = C(n,1) + C(n,2) + C(n,3), or n*(n^2 + 5)/6.at n=31A004006
- a(n) = n! - n^2.at n=7A005008
- Lucas-Carmichael numbers: squarefree composite numbers k such that p | k => p+1 | k+1.at n=4A006972
- Orders of cyclotomic polynomials containing a coefficient the absolute value of which is >= 4.at n=37A013592
- a(n) = Sum_{ d|n } sigma(n/d)*d^4.at n=7A027848
- 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 69.at n=22A031567
- Number of partitions satisfying cn(0,5) + cn(1,5) <= cn(2,5) and cn(0,5) + cn(1,5) <= cn(3,5) and cn(0,5) + cn(4,5) <= cn(2,5) and cn(0,5) + cn(4,5) <= cn(3,5).at n=41A039882
- Numbers whose base-4 representation contains exactly two 1's and four 3's.at n=16A045123
- If p | n, then p+1 | n+1 for composite n.at n=28A056729
- Number of 3 X 3 matrices, with elements from {0,...,n}, having the property that the middle element of each of the eight 3-element horizontal, vertical and diagonal lines equals the average of the two end elements.at n=30A059329
- Composite numbers not divisible by 2, 3 or 5 which contain their largest prime factor as a substring in base 2.at n=36A063137
- Numbers k such that reverse(gpf(k)) = gpf(k+1), where gpf(n) = A006530(n); a(1)=1.at n=14A071844
- Values of n corresponding to the terms in sequence A080155. For any k, the concatenation of the a(1) to a(k)-th primes is prime and each value of k is the smallest for which this is true.at n=43A080156
- Nonprimes k that divide (Fibonacci(k^2)-1).at n=39A086504
- Numbers k such that R(k+9) = 5.at n=2A086949
- Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n-1) - 63 for n > 0.at n=13A101824
- A sequence of asymptotic density zeta(8) - 1, where zeta is the Riemann zeta function.at n=20A143034
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 0, 0), (0, -1, 1), (0, 1, -1), (1, 1, 1)}.at n=7A149700
- Odd squarefree numbers n such that the cyclotomic polynomial Phi(n,x) has height 4.at n=18A152942