Sample to config Episerver TinyMCE editor to use numeric entity encoding (code snippet from alloy config).

ExtendedTinyMceInitialization.cs

using EpiWithSearch.Models.Blocks;
using EpiWithSearch.Models.Pages;
using EPiServer.Cms.TinyMce.Core;
using EPiServer.Framework;
using EPiServer.Framework.Initialization;
using EPiServer.ServiceLocation;

namespace EpiWithSearch.Business.Initialization
{
    [ModuleDependency(typeof(TinyMceInitialization))]
    public class ExtendedTinyMceInitialization : IConfigurableModule
    {
        public void Initialize(InitializationEngine context)
        {
        }

        public void Uninitialize(InitializationEngine context)
        {
        }

        public void ConfigureContainer(ServiceConfigurationContext context)
        {
            context.Services.Configure<TinyMceConfiguration>(config =>
            {
                // Add content CSS to the default settings.
                config.Default()
                    .ContentCss("/static/css/editor.css")
                    // global config to use numeric encoding, see last line if you only need
                    // it for one property on a type
                    .AddSetting("entity_encoding", "numeric");

                // add settings to tinymce
                config.Default()
                    .AddPlugin("code charmap")
                    .AppendToolbar("code charmap");

                // OR use numeric encoding only for a specific types field
                config.For<StandardPage>(t => t.SpecialField).AddSetting("entity_encoding", "numeric");
            });
        }
    }
}