1681
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 16
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 3
- Divisor Sum
- 1723
- Proper Divisor Sum (Aliquot Sum)
- 42
- 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
- 1640
- Möbius Function
- 0
- Radical
- 41
- Omega Function (Ω)
- 2
- Little Omega Function (ω)
- 1
Special
- Factorial
- no
- Catalan Number
- no
- Bell Number
- no
- Motzkin Number
- no
- Primorial
- no
Figurate Numbers
- Fibonacci Number
- no
- Triangular Number
- no
- Perfect Square
- yes
- 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
- no
- Prime Power
- yes
- Prime Factorization
- no
- Twin Prime
- no
- Mersenne Prime
- no
- Sophie Germain Prime
- no
- Safe Prime
- no
- Powerful Number
- yes
- Achilles Number
- no
- Perfect Power
- yes
- Smooth Number
- no
- Carmichael Number
- no
Classification
- Even
- no
- Odd
- yes
Appears in sequences
- a(n)-th triangular number is a square: a(n+1) = 6*a(n) - a(n-1) + 2, with a(0) = 0, a(1) = 1.at n=5A001108
- Squares of primes.at n=12A001248
- Perfect powers: m^k where m > 0 and k >= 2.at n=51A001597
- Bending a piece of wire of length n+1; walks of length n+1 on a tetrahedron; also non-branched catafusenes with n+2 condensed hexagons.at n=8A001998
- Glaisher's T numbers.at n=2A002439
- Squares and cubes.at n=49A002760
- Erroneous version of A002439.at n=3A002811
- Duplicate of A006253.at n=6A003697
- Divisible only by primes congruent to 6 mod 7.at n=48A004624
- Sum of squares of primes dividing n.at n=40A005063
- Sum of squares of odd primes dividing n.at n=40A005066
- Sum of squares of primes = 2 mod 3 dividing n.at n=40A005075
- Sum of squares of primes = 1 mod 4 dividing n.at n=81A005079
- Sum of squares of primes = 1 mod 4 dividing n.at n=40A005079
- Number of perfect matchings (or domino tilings) in C_4 X P_n.at n=6A006253
- Number of distinct vertex-degree sequences of n-faced polyhedral graphs.at n=8A006869
- Crystal ball sequence for D_4 lattice.at n=4A007204
- Erroneous version of A048798.at n=39A007914
- Coordination sequence T2 for Zeolite Code AEI.at n=31A008002
- Coordination sequence T1 for Zeolite Code FER.at n=25A008106