The Mexico Social Security Number: You need a Mexican Social Security Number in order to apply for the Mexican Social Security Medical Insurance. Apply on line at: http://www.imss.gob.mx/tramites/imss02008 . All you need to have handy is your CURP number, an Email address and a printer. Follow the step by step instructions and you can print out this valuable document in minutes.The document is letter size the above illustration is what the very top of the document looks like.