An Euler number prime is an Euler number 
such that the absolute value 
is prime
(the absolute value is needed since 
takes on alternating positive
and negative values for even
indices). Note that these numbers are distinct from a different type of prime
known as Euler primes.
The first few Euler number primes 
occur for 
, 6, 38, 454, 510, ... (OEIS A103234),
corresponding to 5, 
,
,
... (OEIS A092823).
As of April 2024, the largest known prime Euler number is 
, which has 1062 decimal
digits and was proven to be prime by D. Broadhurst
in 2002. The following table summarizes searches for larger Euler number primes,
of which there are none others up to a limit of at least 
.
| search limit | date | searcher |
| 28688 | Mar. 21, 2009 | E. Weisstein |
| 69574 | Aug. 21, 2020 | S. Plouffe (pers. comm.) |
| 100000 | Feb. 20, 2022 | S. Plouffe (pers. comm.) |
| 112130 | Apr. 15, 2024 | S. Plouffe (pers. comm.) |
