7841
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
- 7842
- 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
- 7840
- Möbius Function
- -1
- Radical
- 7841
- 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
- 52
- 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
- yes
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Prime Index
- 991
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Primes p such that the multiplicative order of 2 modulo p is (p-1)/4.at n=48A001134
- Number of series-reduced rooted trees with n nodes.at n=18A001679
- Numbers that are the sum of 6 nonzero 8th powers.at n=12A003384
- Primes p == 1 (mod 8), p = a^2 +64*b^2 such that y^2 = x^3 + p*x has rank 0.at n=38A007765
- Numbers k such that the continued fraction for sqrt(k) has period 89.at n=6A020428
- Fibonacci sequence beginning 3, 11.at n=15A022123
- a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n+1-k), where k = [ (n+1)/2 ], s = (1, p(1), p(2), ...).at n=23A024479
- a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = [ n/2 ], s = (1, p(1), p(2), ...).at n=22A025099
- Primes of the form k^2 + k + 9.at n=12A027758
- Smallest prime containing n-th square as substring.at n=28A029948
- Smallest nontrivial extension of n-th square which is a prime.at n=27A030685
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 42 ones.at n=34A031810
- Erroneous version of A001679.at n=15A037163
- Primes with indices that are primes with prime indices.at n=38A038580
- Primes prime(k) for which A049076(k) = 3.at n=26A049079
- Primes p such that number of primes produced according to rules stipulated in Honaker's A048853 is 3.at n=13A050665
- Least prime in A031930 (lesser of 12-twins) whose distance to the next 12-twin is 2*n.at n=27A052355
- Primes p such that p-12, p and p+12 are consecutive primes.at n=4A053072
- Number of symmetric types of (3,2n)-hypergraphs under action of complementing group C(3,2).at n=28A055780
- Numbers k such that k^16 == 1 (mod 17^3).at n=24A056088