How do I know if Iam running an amd64 Ubuntu Jackalope

In one of my email to the mailing lists, I indicated that my linux is running on Ubuntu. In their answer, I was queried to say if it is an amd64 Ubuntu Jackalope but I did not know how to find out if it is amd64 Ubuntu Jackalope. I was only able to find that the release is 9.04, codename juanty and uname -r is 2.6.28-11-generic. These are what I found through the command line.
But all these have not attended to the question of amd64 above. Could you please guide me on how to find out the answer.