A number of ways worth trying:
Copy a blank cell, then select your text cell(s) and Edit/ Paste Special/
Add
Put 1 in a spare cell, copy, then select your text cell(s) and Edit/ Paste
Special/ Multiply
Use Data/ Text to Columns

If none of those work, you may have non-breaking spaces or other
non-standard characters with your text, so you may need to identify them and
remove them.
--
David Biddulph

Manikandan wrote:
I have a data 901521 in text format. how can i convert this as a
numeric format to add with other numeric data.