1691
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 17
- Digital Root
- 8
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 1800
- Proper Divisor Sum (Aliquot Sum)
- 109
- 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
- 1584
- Möbius Function
- 1
- Radical
- 1691
- 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
- 135
- 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
- Strobogrammatic numbers: the same upside down.at n=21A000787
- a(n) = floor(Fibonacci(n)/4).at n=20A004697
- a(n) = floor(n*phi^8), where phi is the golden ratio, A001622.at n=36A004923
- a(n) = round(n*phi^8), where phi is the golden ratio, A001622.at n=36A004943
- Number of partitions of n into partition numbers.at n=38A007279
- Coordination sequence T4 for Zeolite Code AFO.at n=27A008018
- Coordination sequence T2 for Zeolite Code AFT.at n=31A008027
- Coordination sequence T1 for Zeolite Code MTT.at n=25A008189
- a(n) = n OR n^2 (applied to ternary expansions).at n=40A008467
- Number of multigraphs with 5 nodes and n edges.at n=11A014395
- Strobogrammatic numbers: numbers that are the same upside down (using calculator-style numerals).at n=45A018846
- Fibonacci sequence beginning 0, 19.at n=11A022353
- Numbers with exactly 5 2's in their ternary expansion.at n=29A023703
- a(n) = [ (2nd elementary symmetric function of S(n))/(first elementary symmetric function of S(n)) ], where S(n) = {first n+1 positive integers congruent to 2 mod 3}.at n=47A024398
- a(n) = floor(Sum_{1<=i<j<=n} (sqrt(j)-sqrt(i))^2).at n=30A025196
- Numbers that are the sum of 3 nonzero squares in exactly 10 ways.at n=39A025330
- a(n) = (d(n)-r(n))/5, where d = A026060 and r is the periodic sequence with fundamental period (0,0,1,4,0).at n=28A026062
- a(n) = T(2n-1,n), where T is the array defined in A026082.at n=5A026088
- 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=26A028423
- 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 41.at n=2A031539