What are the password requirements for an admin password??

Hi during an upgrade Netgear forced me to change my admin password. It didn't like my combo of letters/numbers. Can someone please tell me what the reqs are? If someone could go in thru advanced and change password and put all lower case letters in and let it gripe and let me know what it wants it might jog my memory. I thought roboform saved it but did not. I do not want to do a factory reset as I have too many settings that need to be changed and I can't remember all of them! Thanks!