DouKaku?

def yakusu(n)
  r = [1,1] #--- hash seed
  s = 2
  while n >= s
    while n%s > 0
      if s * s > n #--- can't divide
        s = n
        break
      end
      s += 1
    end
    r += r.map {|x|x * s}
    n /= s
  end
  Hash[*r].values #--- to uniq
end

def kanzen(n, m)
  r = []
  (1..n).each {|x|
    r << x if (m * x == yakusu(x).inject(0){|sum,a|sum + a})
  }
  r
end

p kanzen(10**2, 2) == [6, 28]  #  => true
p kanzen(10**4, 3)             #  => [120, 672]