A fun number game

Here’s a fun number game:

For any U.S. president, collect three numeric digits as follows:

— One digit is the number of letters in their first name.
— One digit is the lowest digit of their birth month.
— One digit is the lowest digit of their birth year.

For example, for Abraham Lincoln, the three digits would be 7, 2 and 9 (for Abraham, February and 1809, respectively).

Now try to form numbers by arranging those digits in different ways. For Lincoln, you get six numbers:

      279, 297, 729, 297, 927, 972

You can do this with any U.S. president. For George Washington, the digits would be 6, 2 and 2. So you only get three numbers:

      226, 262, 622

So some presidents produce six numbers, and others produce three. Yet among the 45 U.S. presidents, only one produces a single number.

But that number might say a lot about that president. Can you figure out what the number is?