11111...77777 (24-digits)

This number is a composite.

                                                  1111 1133333355 5555777777

The integer 111111333333555555777777, made entirely from nondescending odd digits, factors into primes made entirely from nondescending odd digits: 111111 333333 555555 777777 = 3 x 7 x 11 x 13 x 37 x 1000003000005000007. [Post]