This number is a prime.
Concatenating the 4th powers of the first two primes of the form 4n+1 (i.e., 5^4 and 13^4) is a prime of the form 4n+1. [Post]
Concatenating the 4th powers of the first two primes of the form 4n+1 (i.e., 5^4 and 13^4) is a prime of the form 4n+1. [Post]