6649
domain: N
Properties
Digital Properties
- Digit Count
- 4
- Digit Sum
- 25
- Digital Root
- 7
- Palindromic Number
- no
- Repdigit
- no
- Automorphic
- no
- Kaprekar Number
- no
- Multiplicative Persistence
- 3
Divisibility
- Divisor Count
- 4
- Divisor Sum
- 6820
- Proper Divisor Sum (Aliquot Sum)
- 171
- 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
- 6480
- Möbius Function
- 1
- Radical
- 6649
- 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
- 168
- 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
- Generalized Fibonacci numbers A_{n,3}.at n=31A006208
- a(0) = 1, a(n) = 23*n^2 + 2 for n>0.at n=17A010013
- Partial sums of binary rooted tree numbers.at n=15A014167
- Number of squares on infinite chessboard at <= n knight's moves from a fixed square.at n=22A018836
- Numbers k such that the continued fraction for sqrt(k) has period 29.at n=15A020368
- Numbers whose base-9 representation has exactly 5 runs.at n=6A043634
- Geometric mean of the digits = 6. In other words, the product of the digits is = 6^k where k is the number of digits.at n=36A061429
- Expansion of (1-x)^(-1)/(1+x-x^2-2*x^3).at n=36A077901
- Number of legal Go positions on a 1 X n board (for which 3^n is a trivial upper bound).at n=8A102620
- Semiprimes with semiprime digits (digits 4, 6, 9 only).at n=24A107342
- Numbers n with property that A077116(n) is nonzero square.at n=32A154101
- Nonprimes formed by concatenation of the decimal digits of a nonprime and its index.at n=41A154507
- Number of ways to place zero or more nonadjacent 1,0 1,1 2,0 2,2 3,0 4,0 5,1 5,2 polyhexes in any orientation on a planar nXnXn triangular grid.at n=7A155434
- Positive numbers y such that y^2 is of the form x^2+(x+199)^2 with integer x.at n=8A159548
- Triangle read by rows: a(1,1) = 1. a(m,m) = sum of all terms in rows 1 through m-1. a(m,n) = a(m-1,n) + (sum of all terms in rows 1 through m-1), for n < m.at n=26A159927
- Number of "ON" cells after n-th stage in simple 2-dimensional cellular automaton (see Comments for precise definition).at n=45A160117
- The initial decimal digits of 2^a(n) are the decimal digits of n followed by n.at n=34A171652
- Products of exactly two Pillai primes.at n=38A181414
- Numbers such that the sum, sum of the squares, and sum of the cubes of the decimal digits are each a perfect square.at n=39A197129
- Number of zero-sum -3..3 arrays of n elements with first through third differences also in -3..3.at n=8A202506