dr. bill: interestingly, the web sources differ on the probability of being dealt a single-suited bridge hand. One asserts the chance is one in 635 billion; another claims one in 6¼ billion.

http://www.csicop.org/si/9809/coincidence.html, a bit over half-way down
http://www.jwu.edu/artnsci/math/duston/stats/homewrk/shmwk3.html, questions 13 and 14

Calculating it, I get the former, one in 635,013,559,600.
[= (52 x 51 x 50 ... 40) ÷ (1 x 2 x 3 x ... 13)]