text: what two prime numbers that, if multiplied, would generate a 400 digit  number?   here are two 200-digit primes whose product has 400 digits.  50000 . . . 00117 (fill in 190 zeroes in the middle) 70000 . . . 00039 (fill in 190 zeroes in the middle)  there are far more possible pairs of such primes than there are quarks in the whole universe.