15155
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 17
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 8
- Divisor Sum
- 20832
- Proper Divisor Sum (Aliquot Sum)
- 5677
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10368
- Möbius Function
- -1
- Radical
- 15155
- 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
- 84
- 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
- Let A(n) = #{(i,j,k): i^2 + j^2 + k^2 <= n}, V(n) = (4/3)*Pi*n^(3/2), P(n) = A(n) - V(n); A000092 gives values of n where |P(n)| sets a new record; sequence gives A(A000092(n)).at n=15A000413
- Fibonacci numbers written in base 8.at n=20A004691
- Expansion of Product_{m>=1} (1+x^m)^8.at n=8A022573
- a(n) = (d(n)-r(n))/2, where d = A026066 and r is the periodic sequence with fundamental period (1,0,0,0).at n=44A026067
- Triangle read by rows: T(n,k) is the number of hill-free Dyck paths of semilength n and having k peaks at odd levels (0<=k<=n-2; n>=2). A hill in a Dyck path is a peak at level 1.at n=59A114586
- a(n+1) -+ a(n) = prime, a(n+1)*a(n) = average of twin prime pairs, a(1)=1, a(2)=6.at n=42A154494
- Triangle of coefficients of p(x,n) = (1/4)*(1-x)^(n+1)*Sum_{m >= 0} ((2*m- 1)^n - (2*m+3)^n)*x^m, read by rows.at n=34A154852
- Integers of the form 4n+3 for which Sum_{i=1..u} J(i,4n+3) obtains value zero exactly 7 times, when u ranges from 1 to (4n+3). Here J(i,k) is the Jacobi symbol.at n=20A166057
- Product plus sum of five consecutive nonnegative numbers.at n=5A173044
- G.f. satisfies: A(x) = (1+x*A(x)^2)*(1+x^2*A(x)^2)*(1+x^3*A(x)^2).at n=8A211854
- Least k such that k*6^n-1 , k*6^n+1, and 2*k*6^n-1 are prime; that is, twin primes and a Sophie Germain prime.at n=31A212481
- Total number of parts of multiplicity 6 in all partitions of n.at n=41A222706
- Permutation of natural numbers: a(n) = A243283(A122111((2*n)-1)).at n=36A244984
- a(n) = Position of 2^n among the numbers which are divisible by the square of their highest noncomposite factor (i.e., the union of {1} and A070003), 0 if not there.at n=21A244986
- Coefficient of x^n in Product_{k>=1} (1+x^k)^n.at n=8A270913
- Numbers using only digits 1 and 5.at n=41A276037
- Numbers k such that 5*10^k + 21 is prime.at n=20A281839
- a(n) = Fibonacci(n) represented in bijective base-8 numeration.at n=19A282239
- Solution of the complementary equation a(n) = 2*a(n-1) - a(n-3) + b(n-1), where a(0) = 1, a(1) = 3, a(2) = 5, b(0) = 2, b(1) = 4, b(2) = 6, and (a(n)) and (b(n)) are increasing complementary sequences.at n=15A295614
- Number of partitions of n into at most 2 copies of 1, 3 copies of 2, 4 copies of 3, ... .at n=42A303939