15105
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 12
- Digital Root
- 3
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 1
Divisibility
- Divisor Count
- 16
- Divisor Sum
- 25920
- Proper Divisor Sum (Aliquot Sum)
- 10815
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 7488
- Möbius Function
- 1
- Radical
- 15105
- Omega Function (Ω)
- 4
- Little Omega Function (ω)
- 4
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
- 133
- 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
- a(n) is the concatenation of n and 7n.at n=14A009441
- a(n) = b(n) - c(n) where b(n) is the n-th Lucas number greater than 3 and c(n) is the n-th number not in sequence b( ).at n=17A014252
- a(n) = (d(n)-r(n))/2, where d = A026057 and r is the periodic sequence with fundamental period (0,0,1,0).at n=49A026058
- Average of terms in n-th row of A077529.at n=17A077532
- Primitive elements of A119432.at n=33A119433
- Numbers k such that k and k+1 have 4 distinct prime factors.at n=12A140078
- Number of nonprime parts in the last section of the set of partitions of n.at n=33A144121
- Row sums of triangle A145364 (S1hat(-2)) and partition array A145363 (M31hat(-2)).at n=22A145365
- G.f.: q-sinh(x) evaluated at q=-x.at n=40A198202
- Numbers whose sum of triangular divisors is also a divisor and greater than 1.at n=20A209311
- Rectangular array A(n, k) = hypergeom([-k, k + n/2 - 1], [1], -4) with row n >= 0 and k >= 0, read by ascending antidiagonals.at n=25A300945
- Numbers k such that k and k+1 are the product of exactly four distinct primes.at n=6A318896
- Numbers k such that k and k+1 each have at least 4 distinct prime factors.at n=12A321504
- G.f. A(x) satisfies A(x) = (1 + x / (1 - x*A(x))^3)^3.at n=6A365122
- Triangle read by rows: T(n,k) is the total number of bubbles of size k found in linear chord diagrams on 2n vertices.at n=47A367000
- a(n) = Product_{(s - 2)|n, s prime} s if n > 0, a(0) = 1.at n=51A368117