11131...99721 (44-digits)

This number is a prime.

                            1113 1719232931 3741434753 5961677173 7983899721

The smallest prime starting with all the 2-digit primes. [Beedassy]

This prime also contains a mnemonic trick. It can be read in the following way: the two-digit primes 11, 13, 17,...,97, are 21 in number. [Silva]