2661
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
- 3552
- Proper Divisor Sum (Aliquot Sum)
- 891
- 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
- 1772
- Möbius Function
- 1
- Radical
- 2661
- 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
- 53
- 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) = ceiling(n*phi^9), where phi is the golden ratio, A001622.at n=35A004964
- Numbers k such that (2^(2k+1) - 2^(k+1) + 1)/5 is prime.at n=13A006596
- Coordination sequence T1 for Zeolite Code ATT.at n=37A008041
- Numbers k such that the continued fraction for sqrt(k) has period 72.at n=2A020411
- a(0) = 1, a(1) = 0, a(n+1) = 2*a(n) + (2*n-1)^2*a(n-1).at n=6A024200
- 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 34.at n=20A031532
- Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 32 ones.at n=6A031800
- Lucky numbers with size of gaps equal to 8 (upper terms).at n=28A031891
- "AFK" (ordered, size, unlabeled) transform of 2,1,1,1,...at n=20A032006
- Numbers k such that the string 7,6 occurs in the base 9 representation of k but not of k-1.at n=35A044320
- Numbers n such that string 6,1 occurs in the base 10 representation of n but not of n-1.at n=29A044393
- Numbers n such that string 7,6 occurs in the base 9 representation of n but not of n+1.at n=35A044701
- Numbers n such that string 6,1 occurs in the base 10 representation of n but not of n+1.at n=29A044774
- Numbers whose base-4 representation contains exactly three 1's and three 2's.at n=18A045103
- List of binary palindromes of even length (written in base 10).at n=41A048701
- a(n)=T(n,n+3), array T as in A049735.at n=19A049743
- a(n)=T(n,2), array T as in A049735.at n=29A049745
- Numbers k such that 129*2^k-1 is prime.at n=28A050590
- Numbers n such that 207*2^n-1 is prime.at n=19A050855
- Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 24.at n=14A051965