Bluebulb Projects' The Measure of Things presents:
3,500 is about 700 times the number of Living U.S. Presidents.
In other words, the count of Living U.S. Presidents is 0.001 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)