That depends on what compression method you use to encode the data your memorising. Some of the best techniques for memorising pi (if i remember correctly) involve a series of pseudo formulae (they only hold for a certain finite number of digits) that generate x digits of pi.

Your then only holding the number of decimal places your at and the formula your using in memory, and speaking out the next digit in your loop ( assuming the person listening only wants them one at a time ).

Using one of these formula you could iterate through, then switch to another...thats pretty mathematical imo.

Now, I, even I, would celebrate (3.14159)
In rhymes inept, the great (26535)
immortal Syracusan, rivaled nevermore (8979)
Who in his wondrous lore, passed on before (32384626)
Left men his guidance how to circles mensurate. (4338327)

--A.C. Orr

This and some other pi stuff (and other cool stuff, too) can be found in 777 Mathematical Conversation Starters, by John dePillis. It only has the first 500 digits of pi listed in that book, though.