Can I get the last 4 digits of a regex credit card number?

It can be 16 digit credit card or more so you can match it using this regex or You can goto This Link and generate your own regex

Regex  (?i)^((d+s+?d+s+?d+s+?)(d{4}))

In here accessing the Group2

                var Creditcardno= // Here put your credit card no
                string reg = @"(?i)^((d+s+d+s+d+s+)(d{4})))";
                Regex r = new Regex(reg, RegexOptions.IgnoreCase);
                Match m = r.Match(Creditcardno);
                int number = m.Groups[2];

You Can get last Four no or anything with grouping the regex.

If you only need last four-digit nothing more

      (.+)([0-9]{4}$) 

use this and from a group1 you can get the last four no.

Here's a pattern to match the last four digits of an American Express card number.

Pattern

3[47]d{2}s?d{6}s?d(d{4})

See the demo here.

Edit: Per request in the discussion we had in the chat, here's a consolidated pattern based on the patterns of most major card networks that you provided (without any research on the specification myself): consolidated pattern

Sources

• Anatomy of a Credit Card: Cardholder Name, Number, Network and More
• ISO/IEC 7812-1:2017 - Identification cards — Identification of issuers — Part 1: Numbering system