Spell out numbers. Fiction isn’t journalism; different standards apply. (The Chicago Manual of Style advises that, in nontechnical contexts, numbers from zero to one hundred be spelled out. There are special exceptions to this rule, but none of them apply here.)
Hyphenate numbers such as twenty-two, and hyphenate compound adjectives such as fourteen-year-old.
Twenty-two years ago, her fourteen-year-old brother went missing at the carnival. Today he came back.