# 1301

This number is a prime.

The sum of all 3-digit PPDI's in base 10 (153, 370, 371, and 407) is prime. [Rupinski]

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 emirp p such that 2^p+p^3 is prime. [Loungrides]

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]

The sum of prime factors (with multiplicities) for the middle number in the smallest nontrivial eRAT triple. [Resta]

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]

The smallest Honaker prime for which the difference between it and its prime index (212) is a square (33^2). [Gaydos]

Halley's Comet appeared in 1301 and served as a model for Giotto's 'Star of Bethlehem'. [Scrovegni]