Hello, I found an issue here.
https://github.com/exceljs/exceljs/blob/master/lib/csv/csv.js#L71

At this line, if we get the string such as 6E10000, then datumNumber would be Infinity but still return it because !Number.isNaN(datumNumber) is true so we can't open the generated excel file.

const str = '6E10001';
console.log(Number(str)); // Inifinity

So we should add one more condition, so the condition should be

if (!Number.isNaN(datumNumber) && datumNumber !== Infinity) {
  return datumNumber;
}

If people agree with this, I want to make a PR for this. thanks!