A prime number which is also a palindrome. I don't think there's any mathematical significance; it's just a curiosity.

In base 10, the first twenty palindromic primes are:

2, 3, 5, 7, 11, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929