7681
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
- 4
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 7682
- 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
- 7680
- Möbius Function
- -1
- Radical
- 7681
- 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
- 176
- 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
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 974
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- tanh(arcsin(tan(x)))=x+1/3!*x^3+1/5!*x^5+1/7!*x^7+7681/9!*x^9...at n=4A012082
- Numbers with exactly 7 1's in their ternary expansion.at n=26A023698
- Numbers whose least quadratic nonresidue (A020649) is 13.at n=22A025025
- Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted then there are a pair of central terms both equal to 6.at n=27A031419
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 72 ones.at n=4A031840
- Primes that are concatenations of n with n + 5.at n=6A032628
- Smallest prime of form 2^n*k + 1.at n=9A035089
- Number of 6-ary rooted trees with n nodes and height exactly 7.at n=14A036645
- Denominators of continued fraction convergents to sqrt(389).at n=11A041739
- Numbers whose base-5 representation contains exactly three 1's and three 2's.at n=18A045232
- Primes of the form n*2^phi(n)+1 with phi the Euler function.at n=11A046154
- Primes p with property that p concatenated with its emirp p' (prime reversal) forms a palindromic prime of the form 'primemirp' (rightmost digit of p and leftmost digit of p' are blended together - p and p' palindromic allowed).at n=39A054217
- a(n) is the least prime p such that p-1 is divisible by 2^n and not by 2^(n+1).at n=9A057775
- Primes p such that p^8 reversed is also prime.at n=39A059701
- Primes with 17 as smallest positive primitive root.at n=10A061329
- Primes p such that the greatest prime divisor of p-1 is 5.at n=28A061599
- Primes of the form floor((8/7)^k).at n=12A067909
- Smallest prime p with bigomega(p-1)=n, where bigomega(m)=A001222(m) is the number of prime divisors of m (counted with multiplicity).at n=11A073919
- a(n) = 512*n + 1.at n=15A076338
- Primes of the form 512*k+1.at n=0A076339