8821
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
- 2
- Divisor Sum
- 8822
- Proper Divisor Sum (Aliquot Sum)
- 1
- 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
- 8820
- Möbius Function
- -1
- Radical
- 8821
- Omega Function (Ω)
- 1
- Little Omega Function (ω)
- 1
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
- 47
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- yes
- Composite Number
- no
- Semiprime
- no
- Squarefree Number
- yes
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- yes
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1099
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- From a Goldbach conjecture: records in A185091.at n=48A002092
- Number of rooted trees with 3 nodes of disjoint sets of labels with union {1..n}. If a node has an empty set of labels then it must have at least two children.at n=7A005173
- Let q_k = p*(p+2) be product of k-th pair of twin primes; sequence gives values of p+2 such that (q_k)^2 > q_{k-i}*q_{k+i} for all 1 <= i <= k-1.at n=44A021007
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 84 ones.at n=1A031852
- "EFK" (unordered, size, unlabeled) transform of 1,3,5,7,...at n=15A032304
- Number of partitions satisfying cn(1,5) <= cn(0,5) and cn(4,5) <= cn(0,5).at n=42A039862
- Replacing digits d in decimal expansion of n with d^3 yields a square.at n=10A048391
- Primes p such that the greatest prime divisor of p-1 is 7.at n=41A061638
- Numbers k such that A048138(k) is a prime and sets a new record for such primes.at n=30A064440
- a(n) is the smallest k such that (k^3 + 1)/(n^3 + 1) is an integer > 1.at n=20A065964
- Centered 14-gonal numbers.at n=35A069127
- Number of 3 X 3 X 3 magic cubes with sum 3n.at n=7A070302
- Primes of the form 210n + 1.at n=19A073102
- Balanced primes of order four.at n=9A082079
- a(n) = 10*n^2 - 6*n + 1.at n=29A087348
- Magnanimous primes: primes with the property that inserting a "+" in any place between two digits yields a sum which is prime.at n=45A089392
- Largest n-digit member of A089392, or 0 if there is no such n-digit term.at n=3A089394
- Primes p such that (p-11)/10 is also a prime.at n=39A089442
- Beginning with 3, least prime, greater than the previous term, such that the arithmetic mean of first n terms is a prime.at n=25A090918
- Balanced primes (A090403) of index 2.at n=43A096706