An event can have a maximum of 500 invitees. However, an invitee can be either an individual or a Google group. You can therefore invite up to 500 groups, allowing for a virtually unlimited number of attendees.
Register Hereor login if you are already a member
In lotus notes 8.5.3 , hence you can call invitees as a single group
Maximum number of contacts allowed in a group in Contacts
32K of names in the Members text field