1685
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 20
- Digital Root
- 2
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 2
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 2028
- Proper Divisor Sum (Aliquot Sum)
- 343
- 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
- 1344
- Möbius Function
- 1
- Radical
- 1685
- 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
- 42
- 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
- Numbers m such that Fibonacci(m) ends with m.at n=39A000350
- Coefficients for numerical integration.at n=4A002686
- a(n) = floor(n*phi^14), where phi is the golden ratio, A001622.at n=2A004929
- Sum of squares of primes = 2 mod 3 dividing n.at n=81A005075
- Coordination sequence T1 for Zeolite Code AFO.at n=27A008015
- Coordination sequence T4 for Zeolite Code HEU.at n=27A008119
- Coordination sequence T7 for Zeolite Code PAU.at n=30A008225
- Coordination sequence T8 for Zeolite Code PAU.at n=30A008226
- Second-order Fibonacci numbers.at n=14A010049
- Numbers k such that the continued fraction for sqrt(k) has period 5.at n=39A010337
- Coefficients in expansion of sqrt(2) as Sum_{n>=1} a(n)/(n*n!*(n+1)!), as found by greedy algorithm.at n=41A011193
- a(n) = floor(n*(n-1)*(n-2)/16).at n=31A011898
- Least d for which the number with continued fraction [n,n,n,n...] is in Q(sqrt(d)).at n=40A013946
- Quadruples of different integers from [ 1,n ] with no common factors between triples.at n=16A015625
- Positive integers n such that 2^n == 2^5 (mod n).at n=52A015925
- a(n) = a(n-1) + a(n-2) + 1 for n > 1, a(0)=1, a(1)=5.at n=13A022319
- Place where n-th 1 occurs in A023119.at n=35A022781
- Numbers k such that Fibonacci(k) == -5 (mod k).at n=46A023165
- a(n) = sum of the numbers between the two n's in A026284.at n=36A026287
- Clog sequence in base 2. Right to left concatenation of n,int(log_2(n)),int(log_2(int(log_2(n)))),... in base 2.at n=20A028423