Salesforce Exported Number fields display in Exponential Format in Spreadsheet (Ex: Excel / Google Sheets)

This behavior has to do with the way the spreadsheet program displays the values of this column. There are a few options to resolve it.

Option 1: Resize the column to at least as wide as the value in the field.

Option 2: Format the column as to match the number of digits in the cell. 

1. Select the cell range that you want to format.
2. On the Format menu, click Custom
3. In the Type box, type a zero for each digit in the number. For example, if the field in your Salesforce org allows 15 digits, then type 15 zeros. 
4. Click OK.

Note: This solution will only work if all the numbers have the same amount of digits. Otherwise Excel will add leading zeros to the number.
 

Option 3: Format the column as Number. 

1. Highlight the column in question.
2. Right click and select Format Cells
3. Choose "Number"
4. Click Ok