389
This number is a prime.
 
An Eisenstein prime with no imaginary part. 
 
The smallest conductor of a rank 2 elliptic curve. 
 
The smallest emirp equal the sum of the first two dozen consecutive idoneal numbers.  [Loungrides]
 
The first in the smallest set of 4 consecutive primes (389, 397, 401, 409) that are congruent to 1 (mod 4).  [Post]
 
The emirp whose common logarithm first exceeds its prime digital root.  [Beedassy]
 
The smallest prime (emirp) whose sum of digits is an abundant number.  [Loungrides]
 
The smallest emirp which is the sum of the digits of first
emirps.  [Silva]
 
The twentieth emirp (389) contains sum of digits equal to twenty.  [Bajpai]
 
The only 3-digit Hyper-Cullen 2nd species prime (emirp),
i.e., a prime of form n*2^n+(n-1), case n=6.  [Loungrides]
 
The only prime (emirp) having 89 as a two-digit ending among the 3-digit primes.  [Loungrides]
 
The product of the first four Fibonacci primes minus one.  [Leonard]