A googolplex is a one followed by a googol zeros, a number too large to write out in full.

The longer version

Put a googol into the exponent instead of the base and you get a one followed by a googol zeros. Writing it out would need more particles than the observable universe contains, even if every particle served as a single digit. Ordinary scientific notation handles it only by nesting powers.

Stacking exponents is what separates the two named giants: a googol is merely a hundred zeros, while a googolplex makes the count of zeros itself a googol. Nothing stops you going further, since adding one always produces something bigger. Such towers are useful mainly as thought experiments about what notation can and cannot express.

Where this entry sits

This section collects odd corners of mathematics, from stubborn prime numbers to counting systems older than modern schools. Expect famous constants, probability puzzles, shapes that break everyday intuition, and numbers far too large to picture. The full list sits on the Numbers and Math page, where every entry is listed in order.