Is Citibank an ACH?

Could you please clarify whether Citibank operates as an Automated Clearing House (ACH)? I understand that ACH is a network that enables financial institutions to electronically transfer funds between accounts, often for transactions such as direct deposits or bill payments. Given Citibank's global reach and extensive financial services, it would seem logical that they would be part of such a network. However, I'm interested in understanding if Citibank specifically functions as an ACH or if they utilize other means for electronic fund transfers. Thank you for your assistance in clarifying this matter.