36558...56701 (39-digits)

This number is a prime.

365586476 5900460618 9047353520 4643656701

The base term of a 38-step pyramid sequence of emirps starting with 31; formed by adding one digit at a time in appropriate inner positions. Discovered by Carlos Rivera and confirmed to be the tallest pyramid of its type:

 31 
311
 3011 
 30161 
 390161 
 3901561 
 39016561 
390163561
 3901763561 
 39061763561 
 390619763561 
3906189763561
 39046189763561 
 390461897563561 
3904601897563561
 39046018975463561 
390460189075463561
 3904601890755463561 
37904601890755463561
 357904601890755463561 
3547904601890755463561
 35547904601890755463561 
355479004601890755463561
 3655479004601890755463561 
36556479004601890755463561
365564790046018907554636561
3655647900460189075546365671
36556479004601890755463656701
365564769004601890755463656701
3655647659004601890755463656701
36556476590046018907554643656701
365564765900460189075354643656701
3655647659004601890753504643656701
36556476590046018907535204643656701
365564765900460618907535204643656701
3655647659004606189073535204643656701
36556476590046061890473535204643656701
365586476590046061890473535204643656701

[Rivera]