1) You will wait a long time for CLUSTER to cope with computations on such a big amount of observations. Consider using FASTCLUS to do the job, or at least create first-level clusters that would be processed afterwards (the two-stage method, I think the correct name for the method is when you look in the SAS help).
2) Use PRINQUAL or CORRESP procedures to pre-process your data : these can create numeric (continuous) variables summarizing information in categorical variables. Then merge with the already existing numeric information. And then cluster.