TheOnlinePhotographer has published a post to celebrate 171717 comments and was amused by the number’s symmetry.

A great comment by Lynn pointed out that this number is indeed an interesting number but not symmetrical.

Symmetrical numbers or words *–* also called palindromes *–* are defined as being the same read forwards or backwards. Examples for palindromic words are *radar*, *noon* or *level*. Palindromic numbers are *3*, *404* or *172271*.

Lynn then went further and checked if 171717 is at least a prime. The number sadly has five distinct prime factors .

So Lynn wondered what the next palindromic prime would be.

To answer this question, I wrote this little Python program to check for palindromic primes. The first 120 palindromic primes are shown below.

Based on this list, the smallest palindromic prime larger than 171717 is **1003001**.

3, 5, 7, 11, 101, 131, 151, 181,
191, 313, 353, 373, 383, 727, 757, 787,
797, 919, 929, 10301, 10501, 10601, 11311, 11411,
12421, 12721, 12821, 13331, 13831, 13931, 14341, 14741,
15451, 15551, 16061, 16361, 16561, 16661, 17471, 17971,
18181, 18481, 19391, 19891, 19991, 30103, 30203, 30403,
30703, 30803, 31013, 31513, 32323, 32423, 33533, 34543,
34843, 35053, 35153, 35353, 35753, 36263, 36563, 37273,
37573, 38083, 38183, 38783, 39293, 70207, 70507, 70607,
71317, 71917, 72227, 72727, 73037, 73237, 73637, 74047,
74747, 75557, 76367, 76667, 77377, 77477, 77977, 78487,
78787, 78887, 79397, 79697, 79997, 90709, 91019, 93139,
93239, 93739, 94049, 94349, 94649, 94849, 94949, 95959,
96269, 96469, 96769, 97379, 97579, 97879, 98389, **98689**,
**1003001**, **1008001**, 1022201, 1028201, 1035301, 1043401, 1055501, 1062601, ...

Thus it takes more comments to reach the closest palindromic prime.

The sequence of palindromic primes is number A002385 in the On-line Encyclopedia of Integer Sequences (OEIS).

```
# Python 2.7.7 Code
# Jonathan Frech 23rd of March, 2016
```

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