8819
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 26
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 8820
- 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
- 8818
- Möbius Function
- -1
- Radical
- 8819
- 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
- no
- Harshad Number
- no
- Narcissistic Number
- no
- Collatz Steps
- 78
- 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
- yes
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 1098
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Smallest prime p==3 (mod 8) such that Q(sqrt(-p)) has class number 2n+1.at n=24A002148
- Let q_k=p(p+2) be product of k-th pair of twin primes; sequence gives values of p such that (q_k)^2 > q_{k-i}q_{k+i} for all 1 <= i <= k-1.at n=44A021005
- 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 93.at n=15A031591
- a(n)^2 is smallest square starting with a string of n 7's.at n=3A034990
- a() = 1,3,... [ A037257 ], differences = 2,... [ A037258 ] and 2nd differences [ A037259 ] are disjoint and monotonic; adjoin next free number to 2nd differences unless it would produce a duplicate in which case ignore.at n=32A037257
- a(n)^2 is the smallest square containing exactly n 7's.at n=4A048352
- Digitally balanced numbers in both bases 2 and 3.at n=20A049361
- a(n) = Sum_{i=0..2n} (-1)^i * T(i,2n-i), array T as in A049723.at n=37A049725
- Endpoints for runs of consecutive primes mentioned in A054691.at n=6A054692
- Integers that can be expressed as the sum of consecutive primes in exactly 4 ways.at n=28A054999
- a(n) is smallest safe prime (A005385) such that a(n) + 12*n is the next safe prime, i.e., x = (a(n) - 1)/2 and x + 6*n are closest Sophie Germain primes.at n=11A059327
- Smaller of twin primes whose middle term is a multiple of A002110(4)=210.at n=10A060230
- Primes p such that p^6 + p^3 + 1 is prime.at n=44A066100
- Primes expressible as the sum of (at least two) consecutive primes in at least 3 ways.at n=14A067379
- Prime sum of n-th group of successive primes in A073684.at n=32A073682
- Safe primes (A005385) (p and (p-1)/2 are primes) such that 12*p+1 is also prime.at n=28A075707
- Near twin primes of order 18: twin primes (p, p+2) such that p+18 and p+20 are primes.at n=21A079304
- Number of irreducible polynomials (over the rationals) of form a*x^2+b*x+c, 1 <= a,b,c <= n.at n=20A079671
- Smallest primes such that a(j) - a(k) are all different.at n=43A079848
- Primes p such that 7 is the largest of all prime factors of the numbers between p and the next prime (cf. A052248).at n=14A080186