To be more specific, it will be four numbers between 1 and 9. There will not be a 0 in an EKA code (obviously, as the method of entry is via turning the drivers door lock, it isn't possible to turn it 0 times). Neither will it contain letters.
It is worth pointing out that the radio codes and the ignition key/lock barrel codes are also four numbers - this is something that has led to confusion in the past where the key ring still carries the grey plastic tag with the key/lock barrel code on it, or someone has written the radio code in the handbook.
If an EKA is unknown, it can be read direct from the ECU by the right diagnostic equipment (this of course has to be done with the vehicle alarm/immobiliser disarmed, so not applicable if you are locked out).