There are exactly 1301 nonisomorphic trees with thirteen vertices. [Patterson]
Bromotrifluoromethane, also known by the trade name Halon 1301, is a colorless, odorless, and non-toxic gas which extinguishes a fire by chemically reacting with the combustion process. It is now known to be environmentally damaging, particularly toward the Earth's protective ozone layer.
The smallest quintan emirp, i.e., an emirp of form (x^5-y^5)/(x-y) for x, y primes, (case x=5, y=2). [Loungrides]
Thirteen zero-one (13:01) is the smallest prime on a 24-hour clock, in hours and minutes, that is displayed as a different prime on a 12-hour clock (1:01) [Homewood]