**URGENT** excel number problem **URGENT** [:)]

Whn I enter a no more thn 15digits , suppose
53124676997564277 , nd press ENTER , the no.
automatically bcoms 53124676997564200….
i.e. Any digit after the 15th one automatically
bcoms 0 or in exponential format..

***I WANNA DISPLAY MORE THN 15 NOS IN A CELL
BUT THIS EXCEL IS RUINING ME****

************* HELP GUYS *****************