How many digit numbers can Microsoft Excel handle?

Default number format in Excel is General therefore you can display up to 11 digits in a cell.

MS Excel can handle 15 digits.

In cells of excel that are formatted as text, you can type up to 32,767 characters, of which Excel displays up to 1,024 characters on the worksheet  you cannot create a custom number format that stores more than 15 digits.

If I type in a 16 digit number (format: number, no decimals) it changes the number on me. Example: 1234567812345678 changes the view to 1234567812345670.

If I type it in as a general format it changes the numbers above so it displays 1.23457E+15 but if you click on the cell, the display shows the last digit as a 0 instead of an 8 once again.

I opened the file on a different computer and same issue now with it. I have changed the auto correction and auto formatting all to no avail. Help!