3119

This number is a prime.

The number of days between the previous terrorist attack on the World Trade Center and 9/11. Note the appearance of 911 in the reversal of 3119.

The smallest prime factor of the 43-digit number of terms required to obtain a sum of 100 in the harmonic series.

The only non-titanic prime of form n^n-6, where n is an integer, (case n=5) [Loungrides]

The smallest right-truncatable prime concatenated from two double-digit primes. [Loungrides]

The smallest of six 4-digit primes of the concatenated form 3AA9 (3119, 3229, 3449, 3559, 3779, 3889). Note that all four-digit numbers of this concatenated form are either prime or divisible by three. [Nie]