8219
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 8220
- 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
- 8218
- Möbius Function
- -1
- Radical
- 8219
- 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
- 189
- 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
- 1030
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes of the form 2^a + 3^b.at n=47A004051
- Expansion of (2-2*x-x^2)/((1-2*x^2)*(1-x)^2).at n=26A016724
- Numbers k such that the continued fraction for sqrt(k) has period 94.at n=20A020433
- 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=43A021005
- a(n+1) = [ A*a(n)+B ]/p^r, where p^r is the highest power of p diving [ A*a(n)+B ] and p=2, A=2.00013, B=3.0.at n=26A029580
- 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 89.at n=29A031587
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 42 ones.at n=36A031810
- Start of a string of exactly 2 consecutive (but disjoint) pairs of twin primes.at n=21A035790
- Numerators of continued fraction convergents to sqrt(771).at n=7A042486
- Primes with first digit 8.at n=39A045714
- a(n) = Sum_{i=0..2n} (-1)^i * T(i,2n-i), array T as in A049723.at n=36A049725
- First of four consecutive primes that comprise two sets of twin primes.at n=33A053778
- Lesser of irregular twin primes.at n=26A060012
- Numbers k such that sigma(k+2) - sigma(k) = prime(k+1) - prime(k).at n=26A067062
- Primes containing 2k digits in which the sum of the first k digits is that of the last k digits.at n=47A068896
- Lowest primes in twin packs.at n=27A069457
- a(0) = 2; a(n) for n > 0 is the smallest prime greater than a(n-1) that differs from a(n-1) by a square.at n=34A073609
- Primes p such that sum of even digits of p equals sum of odd digits of p.at n=39A076167
- Near twin primes of order 12: twin primes p,p+2 such that p+12 and p+14 are primes.at n=32A079292
- a(n) = smallest prime > n*prime(n).at n=42A079779