11821
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 2
- Divisor Sum
- 11822
- Proper Divisor Sum (Aliquot Sum)
- 1
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 11820
- Möbius Function
- -1
- Radical
- 11821
- 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
- 143
- 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
- 1417
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers k such that the continued fraction for sqrt(k) has period 43.at n=31A020382
- Primes p such that p, p+6, p+12, p+18 are all primes.at n=24A023271
- Primes that remain prime through 3 iterations of function f(x) = 4x + 3.at n=28A023281
- Primes that remain prime through 4 iterations of function f(x) = 4x + 3.at n=6A023311
- Denominators of continued fraction convergents to sqrt(283).at n=10A041533
- Numerators of continued fraction convergents to sqrt(869).at n=6A042678
- Sequence of 2 Pythagorean triangles, each with a leg and hypotenuse prime. The leg of the second triangle is the hypotenuse of the first.at n=37A048270
- Number of semiorders on n labeled nodes whose incomparability graph is connected.at n=5A048287
- Second term of strong prime 5-tuples: p(m)-p(m-1) > p(m+1)-p(m) > p(m+2)-p(m+1) > p(m+3)-p(m+2).at n=30A054809
- Primes of the form sum 6d/(2 + mu(d)) for some k and all d dividing k.at n=26A069548
- Initial term in sequence of four consecutive primes separated by 3 consecutive differences each <=6 (i.e., when d=2,4 or 6) and forming d-pattern=[6, 4,2]; short d-string notation of pattern = [642].at n=19A078855
- Primes p such that the differences between the 5 consecutive primes starting with p are (6,4,2,6).at n=3A078962
- Fixed points when A001414 is iterated and started at factorials of prime numbers.at n=53A082086
- Numbers n such that n*359# +-1 are twin primes, where 359# = 72nd primorial (A002110(72)).at n=12A087907
- Balanced primes of order eight.at n=23A096700
- Greater of a,b where n^2 = a^3 + b^3; a,b>0 and gcd(a,b)=1. The lesser of a,b is the corresponding term in A099532 and n, which is used to order this sequence, is the corresponding term in A099426.at n=30A099533
- Squares of the norms of Gaussian primes from A107629.at n=26A107630
- Primes whose SOD and that of their indices are both prime and equal (indices may not be prime, but their SOD must be prime).at n=38A117477
- Least prime p for which Mertens's function M(p) = n.at n=38A123172
- Numbers k such that (9^k + 5^k)/14 is prime.at n=10A128339