How do you verify A Drug Enforcement Agent badge number?

Contact the DEA and ask. Realistic advice: If he shows you a badge and a valid ID folder, I wouldn't try to interfere with his lawful actions if I were you.

WRONG, WRONG, WRONG... I would always ask for ID and I would always verify, especially if they are in plain clothes. It is our right to verify who we are speaking with. They cannot hold that against you. Then they would be breaking the law.