23571...97779 (397-digits)

This number is a probable-prime (likely to be a prime but we have not (re-)proven it on this site).

                         2357137 9393744759 6777989913 7937379957 6779899992
3793945769 7788973373 7795977989 9499444949 7667989959 5557769778 9967679666
7696778979 9779777797 8998888998 8988888999 9999999999 9939233995 6698999397
3955678892 3739379979 8999337937 6778994794 9755978889 9955559597 7989679696
7776799999 7777779788 9888888888 8999999999 9999993277 9956988899 2393744569
3732794579 7889993394 7577788999 4747479777 5559595799 9976677967 7889997779

Just showing those entries submitted by 'Gaydos': (Click here to show all)

The concatenation of the largest digit in each of the first 397 primes is a prime number. [Gaydos]