This can be verified from the factorization
p27 - 1 = 219 . 51309697 . 11878566851267
The fact that p27 - 1 is divisible by 219 is not surprising. Since p27 is a factor of the Fermat number F13, a well-known theorem implies that p27 - 1 is divisible by 215.
Richard Brent
30 June 1995