# 13331

This number is a prime. Inserting any digit d between adjacent digits of this palindromic prime never produces a new prime. [De Geest] The minimum palindromic prime p such that p ± 1 each has exactly 4 distinct prime factors. [Das] The smallest palindromic prime with five embedded primes: 3331, 331, 31, 13 and 3. [Necula] The sum of the squares of three consecutive odd triangular numbers (45^2 + 55^2 + 91^2). Note the three 3's in the middle. [Silva] The smallest palindromic prime in the form 'prime-d-emirp'. '13-d-31' is a palindromic prime for d = 3, 8, and 9. Curiously, 389 is also an emirp. [Green] The largest prime formed by inserting d identical digits d, between two identical digits n, (d=3, n=1). Note that there are only two other such primes; 313 and 919. [Loungrides] The 13331st verse in the Bible (KJV) is the 17771st verse from the end. [Slattery] The smallest expanded palindromic prime, i.e., a palindromic prime obtained from another by repeating its digits in order, each digit repeated d times. [Silva]

(There are 4 curios for this number that have not yet been approved by an editor.)