What is strength of glass?

That depends on how the glass is fabricated and finished and the environment it is in, and the type of glass. In general, and approximately,

For perfect glass fibers, strength is 500,000 psi (3500 MPa).

For polished glass Windows, in air, strength is 7000psi (50MPa)

For scratched glass, 100 micron deep scratch, it is 2500 psi (20 MPa)

For scratched glass in high humidity for several years it is 1000 psi ( 7 Mpa)