Is there any way to describe worker number in each machine?

I know that one way is repeating the hostname N times to have N workers. Is there a way to explicitly say
hostname N ?

You can use a machinefile

Julia can be started in parallel mode with either the -p or the --machinefile options. -p n will launch an additional n worker processes, while --machinefile file will launch a worker for each line in file file. The machines defined in file must be accessible via a passwordless ssh login, with Julia installed at the same location as the current host. Each machine definition takes the form [count*][user@]host[:port] [bind_addr[:port]] . user defaults to current user, port to the standard ssh port. count is the number of workers to spawn on the node, and defaults to 1. The optional bind-to bind_addr[:port] specifies the ip-address and port that other workers should use to connect to this worker.

From https://docs.julialang.org/en/stable/manual/getting-started/#Getting-Started-1

So something like 5*hostname should do the trick.

ah, thanks! did not noticed the documentation! I was looking at the parallel computing section.