A gigantic prime is a prime with 
or more decimal digits.
The first few gigantic primes are given by 
for 
, 55377, 70999, 78571, 97779, 131673, 139579, 236761,
... (OEIS A142587).
Gigantic Prime
See also
Large Number, Probable Prime, Titanic PrimeExplore with Wolfram|Alpha
References
Caldwell, C. "The Ten Largest Known Primes." http://www.utm.edu/research/primes/largest.html#largest.Lifchitz, H. and Lifchitz, R. "PRP Records: Probable Primes Top 10000." http://www.primenumbers.net/prptop/prptop.php.Sloane, N. J. A. Sequence A142587 in "The On-Line Encyclopedia of Integer Sequences."Yates, S. "Collecting Gigantic and Titanic Primes." J. Recr. Math. 24, 193-201, 1992.Referenced on Wolfram|Alpha
Gigantic PrimeCite this as:
Weisstein, Eric W. "Gigantic Prime." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/GiganticPrime.html