18133...33181 (35-digits)

This number is a prime.

                                      18133 3921830933 3727333903 8129333181

Note that (beginning with 2) each successive number below is the smallest palindromic prime to contain the one above as a central substring.

2
727
37273
333727333
93337273339
309333727333903
1830933372733390381
92183093337273339038129
3921830933372733390381293
1333921830933372733390381293331
18133392183093337273339038129333181
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.
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