6781
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
- 6782
- 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
- 6780
- Möbius Function
- -1
- Radical
- 6781
- 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
- 181
- 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
- 873
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Coordination sequence for FeS2-Marcasite, S position.at n=43A009954
- a(n) = M(n) + m(n) for n >= 2, where M(n) = max{ a(i) + a(n-i): i = 1..n-1 }, m(n) = min{ a(i) + a(n-i): i = 1..n-1 }.at n=24A022905
- Primes that remain prime through 3 iterations of function f(x) = 9x + 2.at n=22A023296
- Primes that remain prime through 4 iterations of function f(x) = 9x + 2.at n=9A023324
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 50 ones.at n=15A031818
- Numbers with exactly five distinct base-9 digits.at n=16A031986
- Numerators of continued fraction convergents to sqrt(933).at n=4A042804
- a(n) = Fibonacci(n) OR Fibonacci(n+1).at n=19A051123
- Primes followed by a [10,2,10] prime difference pattern of A001223.at n=12A052376
- Primes p whose period of reciprocal equals (p-1)/5.at n=16A056210
- Primes p such that p^6 reversed is also prime.at n=29A059699
- Primes of the form 2*k*prime(k) + 1.at n=11A062403
- Twin primes belonging to packs of three or more twin pairs.at n=34A069467
- A Fibonacci-like model in which each pair of rabbits dies after the birth of their 4th litter: a(n) = a(n-2) + a(n-3) + a(n-4) + a(n-5).at n=22A072465
- a(1) = 1, then the smallest prime divisor of A065447(n) not included earlier.at n=34A087552
- Primes p such that (p-11)/10 is also a prime.at n=31A089442
- a(n) is least prime p such that 7 is the n-th term in the Euclid-Mullin sequence starting at p, or 0 if no such prime p exists.at n=26A094153
- Balanced primes of order five.at n=20A096697
- Primes p such that the polynomial x^4-x^3-x^2-x-1 mod p has 4 distinct zeros.at n=28A106280
- Primes such that the sum of the predecessor and successor primes is divisible by 23.at n=38A112847