11815
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 15120
- Proper Divisor Sum (Aliquot Sum)
- 3305
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 8832
- Möbius Function
- -1
- Radical
- 11815
- Omega Function (Ω)
- 3
- Little Omega Function (ω)
- 3
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
- 99
- Smith Number
- no
- Vampire Number
- no
Primality
- Prime
- no
- Composite Number
- yes
- Semiprime
- no
- 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
- Numbers n such that phi(n + 1) | sigma(n) for n congruent to 1 (mod 3).at n=30A015817
- Numbers k such that 131*2^k+1 is prime.at n=27A032415
- 23-gonal numbers: a(n) = n(21n-19)/2.at n=34A051875
- Triangle of numbers relating two simple context-free grammars (A052709 and A052705).at n=40A073152
- Pair the odd numbers such that the k-th pair is (r, r+2k) where r is the smallest odd number not included earlier: (1, 3), (5, 9), (7, 13), (11, 19), (15, 25), (17, 29), (21, 35), (23, 39), (27, 45), ... This is the sequence of the product of the members of pairs.at n=26A075320
- Number of orbits of the 4-step recursion mod n.at n=40A106286
- Number of (w,x,y) with all terms in {0,...,n} and w<x+y and x<y.at n=30A212980
- Number of partitions p of n such that (number of distinct parts of p) >= max(p) - min(p).at n=49A239958
- Number of partitions of n such that the number of odd parts is a part.at n=40A240574
- Number of partitions of n with the property that if two summands have the same parity, then their frequencies have the same parity.at n=40A240949
- a(1)=5; thereafter, if n odd, a(n) = a(n-1)-st prime, and if n even, a(n) = a(n-1)-st nonprime.at n=9A280030
- Regular triangle read by rows: T(n,k) is the k-th ionization energy of the n-th chemical element (in kJ/mol), rounded to the nearest integer.at n=5A322834
- Numbers k such that 407*2^k+1 is prime.at n=19A323103
- Odd composite integers m such that A003501(2*m-J(m,21)) == 5 (mod m) and gcd(m,21)=1, where J(m,21) is the Jacobi symbol.at n=40A339522
- Odd composite integers m such that A004254(m-J(m,21)) == 0 (mod m) and gcd(m,21)=1, where J(m,21) is the Jacobi symbol.at n=29A340098
- Triangle read by rows: T(n,k) is the number of oriented graphs on n unlabeled nodes with k arcs, n >= 0, k = 0..n*(n-1)/2.at n=50A350733
- a(n) is the least k such that A366912(k) = n.at n=16A366913
- E.g.f. satisfies A(x) = exp( Integral abs(1/A(x)^2) dx ), where abs(F(x)) equals the series expansion formed by the unsigned coefficients in F(x).at n=7A381361