Through awk and keeping middle column:
awk '{printf("%.f ", ($1/65)+0.5)}1' infile > outfile
24 1533 C_P.doc
11 691 C_M.doc
14 905 G_S.doc
15 945 J_Z.doc
24 1549 J_M.doc
27 1701 L_B.doc
Through awk and without middle column:
awk '{printf("%.f", ($1/65)+0.5); $1=""}1' infile > outfile
24 C_P.doc
11 C_M.doc
14 G_S.doc
15 J_Z.doc
24 J_M.doc
27 L_B.doc