What is the Largest Number in the Universe?

Ever since we start learning to count as kids, a fascinating question inevitably pops up in our minds: What is the biggest number?

Most people will confidently answer "Infinity!" But infinity is not actually a number; it is a concept representing something that goes on forever without end. Furthermore, because numbers are infinite, you can always just add "1" to any number someone claims is the largest.

So, we have to rephrase the question: What is the biggest number we actually know of and have a name for? To answer that, we have to start small and scale our way up.

The Foundation: Understanding Scale

To grasp the true monsters of mathematics, we need a frame of reference. Let's look at the numbers we use every day.

1. One Million (10⁶)

A million is a 1 followed by 6 zeros. It would take you about 12 days to count to a million out loud. We use it daily: real estate prices, city populations, and even the pixels on your screen. If your laptop display is 1280x800, you are staring at roughly one million pixels right now.

2. One Billion (10⁹)

A billion adds three more zeros, but the jump in scale is staggering. While counting to a million takes 12 days, counting to a billion would take you 32 years. We see this scale in global populations (over 8 billion people) and the net worths of modern billionaires.

Related Article: The 8 Largest Objects In The Universe

3. Trillions to Octillions

• Trillion (10¹²): Takes 32,000 years to count to. Often used to measure global economies and national debts.
• Quadrillion (10¹⁵): The estimated number of ants currently crawling on the surface of the Earth.
• Quintillion (10¹⁸): The total number of grains of sand on every beach on Earth. It is also the number of atoms in a single grain of salt.
• Octillion (10²⁷): The number of atoms inside a single human body!

Interactive: The Zeros Visualizer

As numbers get larger, the human brain struggles to comprehend them. Use the interactive slider below to add zeros and see how quickly these numbers escalate past our everyday understanding.

Stepping into the Cosmic Scale

The Observable Universe (10⁸⁰)

If we take a massive leap to a 1 followed by 80 zeros, we reach the estimated number of atoms in the entire observable universe. Think about that: a single human body has more atoms in it than there are sand grains on Earth, yet 10⁸⁰ accounts for every atom in every star, planet, and galaxy we can see.

A Googol (10¹⁰⁰)

A Googol is a 1 followed by 100 zeros. (Yes, the search engine "Google" was named after a misspelling of this math term!). This number is so large that it exceeds the number of atoms in the universe. Because of this, a Googol doesn't have many practical applications in physical science, but it exists in mathematics and probability.

A Googolplex (10^Googol)

What if you take a 1 and add a Googol amount of zeros after it? You get a Googolplex. To put this in perspective: if you tried to write down a Googolplex, and you wrote a zero on every single atom in the universe, you would run out of atoms before you finished writing the number.

A Googolplexian

A Googolplexian is 10 to the power of a Googolplex. There are so many digits in the exponent alone that it is entirely incomprehensible to the human brain.

The True Giants: Graham's and Rayo's Number

Graham's Number

Named after mathematician Ronald Graham, this number is an "upper bound" solution to a complex problem in Ramsey theory. It is so mind-bogglingly vast that standard scientific notation (like 10¹⁰⁰) is completely useless. To even write the equation to solve it, mathematicians had to invent "Knuth's up-arrow notation," where a single arrow indicates massive exponents, and multiple arrows indicate powers stacked upon powers stacked upon powers.

Graham's number is so large that if your brain actually tried to fully comprehend its scale, it would theoretically collapse into a black hole due to the required information density.

Rayo's Number

In 2007, an actual "Big Number Duel" took place at MIT. Mathematicians competed to write the largest number possible on a chalkboard using standard set theory. Agustin Rayo won by creating a formula that essentially bypassed physical counting entirely.

Rayo's Number is defined as: "The smallest number bigger than any finite number named by an expression in the language of first-order set theory with a googol symbols or less."

Rayo's number is so unimaginably huge that Graham's number looks like an absolute zero next to it. Currently, it stands as the champion—the biggest named number we know of.