The number of isomers formed by C6H14 is 5. Isomers are molecules with the same molecular formula but different structural arrangements of their atoms. C6H14 can form five isomers: n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane. The first three are straight-chain isomers, while the last two are branched-chain isomers. These isomers have different physical and chemical properties, such as boiling points, melting points, and reactivities, which make them useful in various industrial applications.