What type of password is better and safer?

I have a iPhone 5c and I have a word password on it right now but I also have the option of a number password what is the best password type to use what will protect my iPhone better?

Number is better

The word passwords are more reliable for keeping people out. I have good enough memory to remember someone's Iphone number password after looking at it just once, but I have a lot harder time figuring out word passwords.

Well, a word password is harder to guess so I would definitely go with that. But pick something that no one would guess easily. Usually, the best passwords are the ones that don't have any real words in them, have capitals mixed in with lower case letters, and have numbers of symbols in them. So things like KEvJEys23Hs or something like that. People are seriously going to have problems guessing that. But most importantly, think of something no one else will be able to guess that you'll be able to remember.

How about using letter and number? I'm using letter and number to lock my phone.

Just the unique one and difficult to guess.

Generally, numbers only should be good enough. If you feel unsafe, then use the text mode and use a mix of numbers and characters. If the login script allows you to use special characters (ie, @ # $ % … Etc.), use one. That should help make up a strong password.

Anyway, keep it short. You may need to access the apps fast for something at given time.