2128
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 13
- Digital Root
- 4
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 20
- Divisor Sum
- 4960
- Proper Divisor Sum (Aliquot Sum)
- 2832
- Abundant Number
- yes
- Perfect Number
- no
- Deficient Number
- no
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 864
- Möbius Function
- 0
- Radical
- 266
- Omega Function (Ω)
- 6
- 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
- 32
- 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
- yes
- Odd
- no
Appears in sequences
- Expansion of 1/((1-x)^2*(1-x^2)*(1-x^3)).at n=39A000601
- a(n) = floor(n*phi^9), where phi is the golden ratio, A001622.at n=28A004924
- a(n) = round(n*phi^9), where phi is the golden ratio, A001622.at n=28A004944
- Central quadrinomial coefficients: largest coefficient of (1 + x + x^2 + x^3)^n.at n=7A005190
- Number of Twopins positions.at n=18A005690
- Quadrinomial coefficients.at n=3A005723
- Generalized Fibonacci numbers A_{n,3}.at n=28A006208
- Coordination sequence T1 for Zeolite Code LOS.at n=32A008132
- Expansion of e.g.f. cos(sinh(x)*sin(x)) in powers of x^4.at n=2A009063
- Expansion of e.g.f.: tanh(log(1+x)/exp(x)).at n=8A009788
- sech(tanh(x)*tan(x))=1-12/4!*x^4+2128/8!*x^8+3482688/12!*x^12...at n=2A012675
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly three 1's.at n=30A013650
- Partial sums of primes, if 1 is regarded as a prime (as it was until quite recently, see A008578).at n=34A014284
- Index of 3^n within sequence of numbers of form 2^i*3^j (A003586).at n=51A022330
- Dying rabbits: a(n) = a(n-1) + a(n-2) - a(n-6).at n=19A023436
- s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (Lucas numbers), t = A014306.at n=27A024477
- s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (Lucas numbers), t = A014306.at n=26A025097
- a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ... + a(n-1)*a(1) for n >= 3.at n=8A025227
- Numbers with 20 divisors.at n=29A030638
- Concatenation of n and n+7.at n=20A032612