74773...54321 (222-digits)

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

                                                               74 7737727717
7076966866 7666665664 6636626616 6065955855 7556555554 5535525515 5054944844
7446445444 4434424414 4043933833 7336335334 3333323313 3032922822 7226225224
2232222212 2021911811 7116115114 1131121111 1019988776 6554433221 1987654321

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

The largest non-titanic prime formed by concatenating in descending order the first n palindromic numbers (case n=83). [Gupta]