The payer's TIN or EIN number isn't 24 characters; it's nine numbers. The difference between the two is that a TIN is a Social Security number that identifies an individual and an EIN is used to identify a company. On your 1099-R, it's located under the payer's name and address in a box that is titled Payer's TIN.
For more information, refer to the IRS articles Taxpayer Identification Numbers (TIN) Employer identification number (EIN).