Encrypted Text Field - Validation Rules - multiple Rules

Question

I am using a encrypted Text Field. List of rules needed:

• Must be able to save a record if value is blank

OR

• Must be Numbers
• Minimum of 10 Digits
• Max of 12 - (implemented with length setting)

What I have Currently 1st Rule:

LEN( Bank_Account_Number__c ) < 10

2nd Rule:

NOT(
    OR( 
        ISBLANK(Bank_Account_Number__c ), 
        ISNUMBER( Bank_Account_Number__c ) 
    ) 
)

How do I format the first rule so that it allows it to be blank also? Or how do I combine them all into one rule?

Bonus Question: Click in field and can't see old data. Type new info in to replace.(cant delete 3 characters and replace) Have to replace entire string.

Thank you for any assistance!

Answer 1

NOT( 
OR( 
ISBLANK( Bank_Account_Number__c ), 
(REGEX( Bank_Account_Number__c , "[0-9]{10}") 
) 
) 
)

Figured it out, answer for those looking