6621
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 15
- Digital Root
- 6
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 8832
- Proper Divisor Sum (Aliquot Sum)
- 2211
- Abundant Number
- no
- Perfect Number
- no
- Deficient Number
- yes
- Highly Composite
- no
- Weird Number
- no
- Untouchable Number
- no
- Primitive Abundant
- no
Derived Values
- Euler's Totient
- 4412
- Möbius Function
- 1
- Radical
- 6621
- 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
- 44
- 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
- a(n) = round(n*phi^16), where phi is the golden ratio, A001622.at n=3A004951
- a(n) = ceiling(n*phi^16), where phi is the golden ratio, A001622.at n=3A004971
- Crystal ball sequence for D_10 lattice.at n=2A008379
- Expansion of e.g.f.: exp(tan(arctanh(x)))=1+x+1/2!*x^2+5/3!*x^3+17/4!*x^4+121/5!*x^5...at n=7A012174
- sinh(tan(arctanh(x)))=x+5/3!*x^3+121/5!*x^5+6621/7!*x^7+636337/9!*x^9...at n=3A012179
- Numbers k such that the continued fraction for sqrt(k) has period 84.at n=15A020423
- Fibonacci sequence beginning 3, 9.at n=15A022379
- Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 54.at n=22A031552
- Lucky numbers with size of gaps equal to 20 (upper terms).at n=13A031903
- Number of flat partitions of n: partitions {a_i} with each |a_i - a_{i-1}| <= 1.at n=54A034296
- Numerators of continued fraction convergents to sqrt(386).at n=7A041732
- a(n)=T(n,n+1), array T as in A049735.at n=32A049741
- Products of distinct terms of 1 and rest from A001566: a(n) = Product_{i=0..floor(log_2(n+1))} L(2^i)^bit(n,i).at n=19A050613
- Products of distinct terms of 1 and rest from A001566: a(n) = Product_{i=0..floor(log_2(n+1))} L(2^i)^bit(n,i).at n=18A050613
- Products of distinct terms of A001566: a(n) = Product_{i=0..floor(log_2(n+1))} L(2^(i+1))^bit(n,i).at n=9A050614
- Number of ordered pairs of integers (x,y) with x^2+y^2 < n^2.at n=46A051132
- Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 24.at n=30A051965
- a(1) = 3; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.at n=41A074339
- Sum_{i=0..2*A053645(n)} (C(2*A053645(n),i) mod 2)*A000045(n-i) [where C(r,c) is the binomial coefficient (A007318) and A000045(n) is the n-th Fibonacci number].at n=19A075149
- Number of iterations of the sine function to be less than 1/n with an initial argument of Pi/2 radians.at n=46A092906