Yes possible, Check out the cases

Case 1: Pre-Set Invoice Number

you can pass Order Reference to MoveName field present in Invoice Obj, which will ensure you get the same number as Invoice Number when you validate. However this method is best suited for 1 Invoice per Sale Order scenarios only. I.e w.r.t Partial Invoicing, chances are high, single SaleOrder can be split & multiple Invoices would be generated, thus during such scenarios, this might possibly fail. Hence in order to have foolproof logic, better to go with Custom Invoice-numbering (case 2)

Case 2: Custom Invoice Number (Highly Recommended)

Upon Validate, Invoice number gets generated & allocated. All you need is, override that method, such that it refers to your Custom-Number.

Tips:

1. As per your requirement, define a Number which is combination of IrSequence & SourceDoc for CustomerInvoice. 

2. Ensure SourceDoc is not edited by any User. Or to be on safer side, you can additionally pass SaleOrder Reference into Invoice, via a separate custom field, use the same to server the purpose.

3. Ensure Custom-Number added in Customer Invoice, doesn't affect other records, such as Customer CreditNote, VendorBills etc.

Hope you got idea.