“There are 1011 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers.”

Spoken as a jest to one of his officers named Gisgo, who had remarked on the numbers of Roman forces against them before the Battle of Cannae (2 August 216 BC), as quoted in A History of Rome (1855), by Henry George Liddell Vol. 1, p. 355
Variant translation: You forget one thing Gisgo, among all their numerous forces, there is not one man called Gisgo.

Source: Group Theory in the Bedroom (2008), Chapter 11, Identity Crisis, p. 206 (See also: George Cantor)

Book III, Ch. 13. Of Experience
Essais (1595), Bartlett's Familiar Quotations, 10th ed. (1919)

When asked to estimate the number of casualties terrorist attacks at the World Trade Center, at a news conference (11 September 2001) http://transcripts.cnn.com/TRANSCRIPTS/0109/11/bn.42.html; this is often misquoted as "More than we can bear."

On Computable Numbers, with an Application to the Entscheidungsproblem (1936)

Source: Drenai series, The King Beyond the Gate, Ch. 16
Context: One hundred only, Lord Earl. But judge us not by our number. Rather, watch the numbers of dead we leave behind.

Diaries of Evelyn Waugh (1976) p. 786

Source: QED: The Strange Theory of Light and Matter (1985), p. 13

"Paul Erdős and the Rise of Statistical Thinking in Elementary Number Theory" https://www.youtube.com/watch?v=5cU0g9dI1S8&t=9m40s (July, 2013) Erdős Centennial Conference, Budapest.