13619
domain: N
Properties
Digital Properties
- Digit Count
- 5
- 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
- 13620
- 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
- 13618
- Möbius Function
- -1
- Radical
- 13619
- 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
- 182
- 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
- 1610
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 58 ones.at n=27A031826
- Primes p whose period of reciprocal equals (p-1)/11.at n=3A056216
- Primes which are the concatenation of numbers n_1, n_2, n_3, in that order, with n_1 + n_2 = n_3 (leading zeros are forbidden for nonzero n_i).at n=19A067860
- a(1) = 1, a(n) = smallest prime number not already used such that concatenation of a(k) and a(n) is composite for all k = 1 to n-1.at n=43A075612
- a(n), for n > 1, equals the least prime p such that p - a(n-1) is a cube, a(1)=2.at n=18A076201
- Record-setting differences between adjacent elements of the Mian-Chowla sequence variant A058335.at n=41A080931
- Primes in which the digit string can be partitioned into three parts such that the sum of the first two is equal to the third, and the second part is nonzero.at n=18A088291
- a(n) = r-th prime of the form (p-q)/(q-r) with r=prime(n+1), q=prime(n+2), and primes p > q.at n=50A089577
- a(n) is the smallest initial value (a prime) for the Euclid-Mullin (EM) sequence in which the p=5 prime emerges as n-th term, i.e., arises at the n-th position.at n=24A093782
- Duplicate of A056216.at n=3A098678
- Primes p such that 2*p+1 and ((2*p+1)^2 + 1)/2 = p^2 + (p+1)^2 are primes.at n=19A098717
- a(n)! is the smallest factorial divisible by the numerator of Sum_{k=0...n} 1/k!, with a(0) = 1.at n=16A102468
- Largest prime factor of numerator of Sum_{k=0...n} 1/k!, with a(0) = 1.at n=16A102469
- Sophie Germain primes for which the reversal is also a Sophie Germain prime.at n=17A118573
- Number of partitions of n into parts with at most one part not greater than 2.at n=46A121659
- Absolute value of second differences of A005849.at n=5A128194
- Least prime P such that 3*p(n)*P*(3*p(n)*P+1)-1, 3*p(n)*P*(3*p(n)*P+1)+1,3*p(n)*P*(3*p(n)*P+3)-1,3*p(n)*P*(3*p(n)*P+3)+1 are all primes with p(i) = i-th prime.at n=36A137839
- An example of a simple prime-generating algorithm similar to Rowland's (A106108) that is a particular instance of a more general algorithm (see comments).at n=37A141537
- Primes congruent to 31 mod 43.at n=38A142280
- Primes congruent to 36 mod 47.at n=35A142387