12819
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 21
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 17096
- Proper Divisor Sum (Aliquot Sum)
- 4277
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8544
- Möbius Function
- 1
- Radical
- 12819
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 2
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
- 125
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- yes
- Squarefree Number
- yes
- Prime Power
- no
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- no
- Achilles Number
- no
- Perfect Power
- no
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- a(n) = [ a(n-1)/a(1) + a(n-2)/a(2) + ... + a(1)/a(n-1) ], for n >= 3.at n=23A022875
- Base 8 digits are, in order, the first n terms of the periodic sequence with initial period 3,1,0,2.at n=4A037776
- Numbers k such that 2^k - 7 is prime.at n=6A059609
- G.f.: Product((1+x^i)/(1-x^i),i=1..n-1)/(1-x^n), with n = 8.at n=24A091779
- Numbers k such that 3*10^k + 8*R_k - 7 is a prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=16A102978
- Numbers n such that p(3n) is prime, where p(n) is the number of partitions of n.at n=47A111389
- Ascending sequence of numbers such that the sum of any two distinct elements (even + odd) is a prime number.at n=31A180743
- Odd nonprimes n such that n+d+1 is prime for all divisors d of n.at n=27A187554
- G.f. satisfies: A(x) = Product_{n>=1} 1/(1 - x^n*A(x)^(n^2)).at n=7A192768
- Record values in A197944.at n=15A197946
- Apparently solves the identity: Find sequence A that represents the numbers of ordered compositions of n into the elements of the set {B}; and vice versa.at n=15A224341
- Smallest m such that gcd(A227113(m+1), A227113(m)) = n.at n=27A227289
- Numbers n which are neither palindromes nor the sum of two palindromes, with property that the largest palindrome which when subtracted from n yields the sum of two palindromes is not the palindromic floor of n (A261423(n)), but rather the next palindrome below that.at n=37A261911
- Numbers k such that k*floor(2^k/k) + 1 is prime.at n=50A270427
- Least number k such that k^2-1 is the sum of two nonzero squares in exactly n ways.at n=15A274567
- Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-2)*b(n), where a(0) = 2, a(1) = 3, b(0) = 1, b(1) = 4, b(2) = 5, and (a(n)) and (b(n)) are increasing complementary sequences.at n=13A296269
- a(n) = N^(1/4) * log(N) / sqrt(log(log(N))) rounded to nearest integer, with N=2^n. Related to operation count of the deterministic factorization of an integer N using an improved Pollard-Strassen method.at n=37A309916
- a(n) = F(n+4) * F(n+1) - 4 * (-1)^n where F(n) = A000045(n) are the Fibonacci numbers.at n=8A341208
- Number of twice-partitions of n into partitions with weakly decreasing lengths.at n=15A358831
- Number of free 4-dimensional polyhypercubes with n cells, allowing corner- and edge-connections.at n=4A365355