A wave on a string is described by

D$($x$,$t$)=(2\mathrm{.}4$cm$)$D$($x$,$t$)=(2\mathrm{.}4$cm$)$

sin$[2$$($x$/(8\mathrm{.}4$m$)+$t$/(0\mathrm{.}16$s$)+1)]$sin$[2$$($x$/(8\mathrm{.}4$m$)+$t$/(0\mathrm{.}16$s$)+1)],$ where xx is in mm and tt is in ss$.$What is the wave number?

Express your answer with the appropriate units.