6691
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
- 2
- Divisor Sum
- 6692
- 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
- 6690
- Möbius Function
- -1
- Radical
- 6691
- 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
- 137
- 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
- 863
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers that are the sum of 6 positive 7th powers.at n=19A003373
- 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=42A021007
- 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 81.at n=11A031579
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 46 ones.at n=20A031814
- Number of partitions of n into parts not of form 4k+2, 24k, 24k+3 or 24k-3. Also number of partitions in which no odd part is repeated, with 1 part of size less than or equal to 2 and where differences between parts at distance 5 are greater than 1 when the smallest part is odd and greater than 2 when the smallest part is even.at n=49A036030
- Number of primes between n*100000 and (n+1)*100000.at n=32A038825
- Primes p such that both p-2 and 2p-1 are prime.at n=40A038869
- Numerators of continued fraction convergents to sqrt(157).at n=8A041288
- Numerators of continued fraction convergents to sqrt(628).at n=4A042204
- Discriminants of imaginary quadratic fields with class number 21 (negated).at n=19A046018
- Primes that yield a different prime when rotated by 180 degrees.at n=25A048890
- Primes of the form 30*p + 1 where p is also prime.at n=20A051646
- The primes in A045574.at n=45A057770
- Primes p such that p^10 reversed is also prime.at n=33A059703
- A list of equal temperaments (equal divisions of the octave) whose nearest scale steps are closer and closer approximations to the ratios of six simple musical tones: 8/7 5/4 4/3 3/2 8/5 7/4.at n=37A060526
- A list of equal temperaments (equal divisions of the octave) whose nearest scale steps are closer and closer approximations to the ratios of 8 musical tones: 8/7 16/11 5/4 4/3 3/2 8/5 11/8 7/4.at n=37A060527
- a(n) = prime(n*(n+1)/2+2).at n=41A078722
- Primes that are still primes when turned upsided down.at n=29A080788
- a(1) = 2; for n > 0, a(n+1) is the a(n)-th prime after a(n).at n=5A093502
- Prime mean of 8 horizontal, vertical and main diagonal sums associated with primes in A094454.at n=6A094455