Bluebulb Projects' The Measure of Things presents:
8,400 is about 2,000 times the number of Living U.S. Presidents.
In other words, the count of Living U.S. Presidents is 0.0005 times that amount.
(a.k.a. Presidents of the United States; a.k.a. Presidents of the United States of America; a.k.a. POTUS), (2016 figures) (including current)
As of this writing, there are five living United States Presidents — President Carter, President Clinton, President Obama, and the two Presidents Bush. At no point in U.S. history have their been more than six (6) living presidents, this circumstance having occurred three times.