rails simple_form Controller#create as HTML

I have a problem with a simple_form_for, if I select many number in my form, I have a rollback, it is not possible to validate.

I have this error:

Processing by SudokusController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"Qafet...", "sudoku"=>{"number"=>"1, 2"}, "commit"=>"Submit"}

but in Terminal (rails c) it's work....

I can not solved this:

_form.html.erb:

<%= simple_form_for @sudoku do |f| %>  
<% (1..9).each do |x| %>
      <div class="checkbox">
        <label>
          <input type="checkbox"name="sudoku[number[]"id="optionsRadios<%= x %>" value="<%= x %>" />
          <%= x %>
        </label>
      </div>
    <% end %>
<% end %>

sudoku.rb:

validates :number, presence: true

in sudoku controller:

def sudoku_params
    params.require(:sudoku).permit(:number)
end

In my db

Sudoku (number:string)

Tanks for your help