In English, the choice between "a" and "an" is determined by the that immediately follows the article, not the spelling.
: "Eleven" starts with a vowel sound (/ɪˈlɛvən/).
The proper indefinite article for "" is " an ." Rule and Reasoning
: Because the first sound is a vowel, you must use " an " (e.g., " I downloaded an 11093.rar file "). Contextual Usage
: The number 11,093 begins with the word " eleven ".