Numbers never end. Thus it is impossible to find the largest Prime number.
The largest known prime number as of 2003 is
m39 = 213,466,917-1
It has 4,053,946 digits and does not fit in this box.
73 is the largest two-digit number that is prime and has prime numbers for both of its digits.
The largest prime number that has 4 digits and begins with a 1 is 1,999.
Smallest is 11 & Largest is 77.
73 is the largest 2 digit number that is both prime and has prime numbers for both of its digits.
It is: 73 of which 7 and 3 are both prime numbers
The largest 3 digit number whose digits are all primes is 777. The largest 3 digit number with different prime digits is 753.
The largest three digit prime number whose digits are all primes is 773.
As of August 2017, the largest known prime number is 2^74,207,281 − 1, a number with 22,338,618digits.I attached a link with the 100 largest known prime numbers, there you can see the number of digits.