13778
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 26
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 6
- Divisor Sum
- 20919
- Proper Divisor Sum (Aliquot Sum)
- 7141
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 6806
- Möbius Function
- 0
- Radical
- 166
- Omega Function (Ω)
- 3
- 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
- 182
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- Squarefree Number
- no
- 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
- yes
- Odd
- no
Appears in sequences
- a(1) = 0, a(2) = -2; for n > 2, a(n) + a(n-2) - a(n-3) - a(n-5) - ... - a(n-p) = (-1)^(n+1)*n if n is prime, otherwise = 0, where p = largest prime < n.at n=56A002120
- Numbers m such that phi(m) * sigma(m) + k^2 is not a square for any k.at n=36A015713
- Shifts left under "AIJ" (ordered, indistinct, labeled) transform.at n=5A032034
- Numbers that, when expressed in base 7 and then interpreted in base 10, yield a multiple of the original number.at n=34A032549
- Numbers that are not squarefree and whose Euler totient function is squarefree.at n=26A049198
- A triangle related to rooted trees.at n=15A060694
- Numbers k that, when expressed in base 7 and then interpreted in base 10, give a multiple of k.at n=35A062944
- Numbers k such that sigma(k)*phi(k) is squarefree.at n=16A065299
- Smallest k not a palindrome and not divisible by 10 such that k and R(k) (A004086) both are divisible by the n-th prime.at n=22A075605
- Maximum number of regions into which the plane can be divided using n (concave) quadrilaterals.at n=42A077591
- a(n) = 2*prime(n)^2.at n=22A079704
- Numbers n such that exp(n) has a smaller relative error abs(exp(n)/m!-1) in approximating the closest factorial m!>1 than exp(k) for any k with 1<k<n.at n=7A101507
- a(n) = Sum_{k=0..n} E2(n, k)*2^k, where E2(n, k) are the second-order Eulerian numbers A340556.at n=5A112487
- 2*p^2, for p an odd prime.at n=21A143928
- Coefficient triangle sequence of a polynomial recursion: p(x,n)=(x + 1)*(p(x, n - 1) + 3^(n - 3)*Sum[x^i, {i, 1, n - 2}]); Row sums approximate 2*3^n.at n=59A153312
- Positions of squares in A048153.at n=12A199551
- Number of idempotent 3X3 0..n matrices.at n=31A222822
- Squares of odd primes and twice squares of odd primes.at n=50A227279
- Even numbers which are neither primes nor perfect powers and are coprime to the sum of their divisors.at n=42A248023
- Composite numbers k such that Sum_{i=1..t-1} d(i+1)/d(i) is prime, where d(1), ..., d(t) are the divisors of k in ascending order.at n=21A255585