Regular Expression for Credit card information should not allow characters
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I am using Regular Expression ^4[0-9]{15}$ for checking Credit card information starting with 4 for VISA and of 16 digits.

But this expression accepts credit card numbers like ‘4141414141414141aa’ which is wrong as it accepts alphabets in the end of a valid credit card number.

Does anyone have any ideas on how to fix this?

Thanks a lot!
