Yes, six is a Scrabble word!
...and is worth 10 points in Scrabble, and 10 points in Words with Friends
six
Adjective
1. Denoting a quantity consisting of six items or units
Noun
1. The cardinal number that is the sum of five and one
2. A playing card or domino or die whose upward face shows six pips
What Scrabble words can I make with the letters in six?
3 Letter Words
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1 Anagram of Six
Words that can be created with an extra letter added to six:
A:axis