Rule of Numbers
Never begin a sentence with a numeric digit. That practice is absolutely forbidden. Either spell out the number or rework the sentence so a word precedes the number.
1. “7.4 in In the Aleutian Trench, registering 7.4, 90 miles south of Unimak Island.”
2. 3C drove the The BMW went with apartment 3C.
3. 107 A hundred and seven young people came.
4. 1956 Nineteen fifty-six was a very good year. (Writers will usually reword the sentence so the date is not at the beginning, but if it is, it must be spelled out.)