What does 解压密码233（19个3）mean?
解压密码 is the password for a zipped file when you need to extract the files.
23333333333 is not a typical chinese word, you can use it as a slang which means LOL. You dont say 23333333333 in your real life just like you dont say LOL in a conversion. It's only intended to express "that's funny" in your social network.
Putting them together, 解压密码233（19个3), it doesnt look like a sentence to me.