15925
domain: N
Properties
Digital Properties
- Digit Count
- 5
- Digit Sum
- 22
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 18
- Divisor Sum
- 24738
- Proper Divisor Sum (Aliquot Sum)
- 8813
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 10080
- Möbius Function
- 0
- Radical
- 455
- Omega Function (Ω)
- 5
- 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
- 27
- 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
- no
- Odd
- yes
Appears in sequences
- Octagonal pyramidal numbers: a(n) = n*(n+1)*(2*n-1)/2.at n=24A002414
- Unitary harmonic numbers (those for which the unitary harmonic mean is an integer).at n=13A006086
- Expansion of 1/((1-2*x)^3*(1-x^2)^2).at n=8A011780
- Expansion of Product_{m>=1} (1+x^m)^7.at n=9A022572
- a(n) = [ 1/(2*t(n+1) - t(n) - t(n+2)) ], where t(n) = tan(Pi/2 - 1/n) satisfies n-1 < t(n) < n for all n >= 1.at n=20A024817
- 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=50A026058
- a(n) = 49*(n-1)*(n-2)/2.at n=24A027469
- Infinitary harmonic numbers: harmonic mean of infinitary divisors is an integer.at n=12A063947
- Numbers k such that sigma(sigma(k)-k) = phi(k).at n=11A074875
- a(n) is the numerator of the probability P(n) of the occurrence of a 3-dimensional self-trapping walk of length n.at n=2A077818
- a(n) = (n+1)*(2*n+1)*(4*n+1).at n=12A079588
- Numbers n such that n is not the power of a prime and such that for every prime divisor p of n, p-1 divides n-1.at n=40A087442
- Where A007535 reaches a record.at n=35A098653
- Structured icosidodecahedral numbers.at n=12A100147
- Numbers k such that 7*10^k + 2*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=12A103053
- Triangle read by rows: T(n,k) is the number of Dyck paths of semilength n and having k ascents of length 4 (0<=k<=floor(n/4)). Also number of ordered trees with n edges which have k vertices of outdegree 4.at n=39A114508
- Row sums of triangle A117425.at n=8A117426
- 13 times the squares: a(n) = 13*n^2.at n=35A152742
- a(n) = 7*a(n-1) + 42*a(n-2), n>2; a(0)=1, a(1)=1, a(2)=13.at n=5A154999
- Positive numbers y such that y^2 is of the form x^2+(x+2401)^2 with integer x.at n=14A157247