What Is the Highest Number in the World?
Integers proceed upward in an infinite sequence, so no number can be said to be the "highest," as it is always possible to add one and get a higher number. Infinity is generally not regarded as a number but as a concept. The highest named number is the googolplex.
A googol is 10^100, or a one with 100 zeros after it. This is 20 orders of magnitude higher than the estimated number of hydrogen atoms in the universe, which makes a googol difficult to use in real-world math. A googol to the googol power, a googolplex, is a one followed by 10^100 zeros. This number can be expressed as 10^10^100. If written in its entirety, however, the sheet of paper it is written on would not fit inside of the observable universe.