Can I be reached on my Apple Watch at a different number as my iphone? Can both numbers reach my Apple Watch?

Your network provider will always assign a number to your Apple Watch SIM. In a properly set up system that number is only used for engineering and administration, the system maps it onto the host iPhone’s number. This means calls from your Apple Watch should be using the iPhone number, and calls to your iPhone will also ring on your watch.

The number assigned to your Apple Watch’s SIM is usually blocked at network level and does not make or originate this own calls.

Branta_uk, is correct. So no, you cannot be reached at the number assigned to your watch, which as suggested is for administration and billing purposes.