15605
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
- 1
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 18732
- Proper Divisor Sum (Aliquot Sum)
- 3127
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 12480
- Möbius Function
- 1
- Radical
- 15605
- 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
- 146
- 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
- Generalized Catalan numbers: a(n+1) = a(n) + Sum_{k=2..n-1} a(k)*a(n-1-k).at n=16A004149
- Triangle of T(n,k)=number of peakless Motzkin paths of length n containing k valleys (can be easily expressed using RNA secondary structure terminology).at n=33A089738
- Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=16A103015
- Largest terms a(n) forming a self-convolution 5th power of an integer sequence (A132840) such that: a(n) <= 5*a(n-1) for n>0 with a(0)=1.at n=6A132839
- Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 0100-1100-0111-0010 pattern in any orientation.at n=14A147047
- a(n) = 54*n^2 - 1.at n=16A158656
- Number of partitions of n containing a clique of size 2.at n=36A183559
- Number of nondecreasing arrangements of 6 numbers x(i) in -(n+4)..(n+4) with the sum of sign(x(i))*2^|x(i)| zero.at n=34A187990
- Triangle read by rows: T(n,k) is the number of peakless Motzkin paths of length n having k UHD's; here U=(1,1), H=(1,0), and D=(1,-1).at n=51A190172
- Number of lattice paths from (0,0) to (n,n) using steps (1,1), (0,2), (2,0), (0,3), (3,0).at n=9A192371
- a(n) is the smallest number that is the sum of both 2n-1 and 2n+1 consecutive primes.at n=25A213174
- Record values in A227617.at n=12A227632
- Index of the smallest prime where n consecutive trailing digits of the index written in binary match n consecutive trailing digits in the prime when written in binary.at n=12A245522
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 113", based on the 5-celled von Neumann neighborhood.at n=28A270179
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 205", based on the 5-celled von Neumann neighborhood.at n=28A270731
- Numbers k(n) used for Markoff forms determining quadratic irrationals with purely periodic continued fractions.at n=18A305311
- G.f.: Sum_{n>=0} (1 + x^n*(1+x)^n)^n * x^n.at n=22A337745