The sequence of large numbers follows a structured Latin-based naming convention that becomes increasingly relevant as science and data technology advance. In the standard short scale system used in the United States and most English-speaking regions, the number that immediately follows sextillion is septillion. While sextillion is represented as 10 to the 21st power ($10^{21}$), or a 1 followed by 21 zeros, a septillion is 10 to the 24th power ($10^{24}$), consisting of a 1 followed by 24 zeros.

To visualize the leap between these two, consider that a septillion is exactly one thousand times larger than a sextillion. In mathematical terms, the transition moves from $1,000,000,000,000,000,000,000$ to $1,000,000,000,000,000,000,000,000$. While these figures seem abstract, they serve as the foundation for measuring everything from the number of atoms in a human body to the total digital data generated by global civilizations.

The progression of naming: Septillion and beyond

The naming of large numbers beyond sextillion follows a predictable pattern based on Latin prefixes. Once the threshold of a million is passed, each new major named number represents a factor of 1,000 greater than the last. This system, known as the "short scale," is the primary method for naming large values in modern finance, physics, and computing.

After septillion, the sequence continues as follows:

  • Septillion: $10^{24}$ (1 followed by 24 zeros)
  • Octillion: $10^{27}$ (1 followed by 27 zeros)
  • Nonillion: $10^{30}$ (1 followed by 30 zeros)
  • Decillion: $10^{33}$ (1 followed by 33 zeros)
  • Undecillion: $10^{36}$ (1 followed by 36 zeros)
  • Duodecillion: $10^{39}$ (1 followed by 39 zeros)
  • Tredecillion: $10^{42}$ (1 followed by 42 zeros)
  • Quattuordecillion: $10^{45}$ (1 followed by 45 zeros)
  • Quindecillion: $10^{48}$ (1 followed by 48 zeros)
  • Sexdecillion: $10^{51}$ (1 followed by 51 zeros)
  • Septendecillion: $10^{54}$ (1 followed by 54 zeros)
  • Octodecillion: $10^{57}$ (1 followed by 57 zeros)
  • Novemdecillion: $10^{60}$ (1 followed by 60 zeros)
  • Vigintillion: $10^{63}$ (1 followed by 63 zeros)

The logic remains consistent. The prefix "sept-" relates to seven, "oct-" to eight, "non-" to nine, and "dec-" to ten. In the short scale, the name of the number is derived from the formula $10^{3(n+1)}$, where $n$ is the value of the Latin prefix. For instance, for septillion (where the prefix relates to 7), the calculation is $10^{3(7+1)} = 10^{24}$.

Conceptualizing the magnitude of a septillion

Human intuition often struggles to differentiate between a trillion, a quadrillion, and a septillion because they all fall under the umbrella of "unimaginably large." However, the physical world provides several benchmarks that help ground these values in reality.

Consider the number of atoms in the human body. An average adult male contains approximately 7 octillion atoms ($7 \times 10^{27}$). This means that if you were looking for a scale that fits the molecular biology of a single human being, you would already be operating three orders of magnitude above a septillion.

In the realm of chemistry, Avogadro's constant—a fundamental value representing the number of constituent particles (usually atoms or molecules) in one mole of a given substance—is approximately $6.022 \times 10^{23}$. This value is just shy of one septillion. Therefore, a single mole of water (about 18 milliliters) contains nearly a septillion atoms of hydrogen and oxygen combined.

In astronomy, the number of stars in the observable universe is often estimated to be around 200 sextillion to 1 septillion. If you were to count every grain of sand on all the beaches of Earth, the total would likely land between 5 and 7 quintillion, which is significantly smaller than a septillion. To reach a septillion, you would need to imagine hundreds of thousands of Earth-like planets, all covered in sand, and sum their grains together.

The Great Confusion: Short Scale vs. Long Scale

A critical factor in understanding what comes after sextillion is the geographical and historical context of number naming. The values discussed above belong to the short scale, which is standard in the US, the UK (since 1974), and most of the English-speaking world.

However, many countries in continental Europe, as well as Spanish-speaking and French-speaking nations, traditionally use the long scale. In the long scale, the name of the number changes every millionfold, not every thousandfold. This creates a massive discrepancy in meaning:

  • Short Scale Billion: $10^9$ (one thousand millions)
  • Long Scale Billion: $10^{12}$ (one million millions—what Americans call a trillion)
  • Short Scale Sextillion: $10^{21}$
  • Long Scale Sextillion: $10^{36}$

In the long scale system, after sextillion comes "sextilliard" ($10^{39}$), followed by "septillion" ($10^{42}$). If you are communicating with international partners in specialized fields, it is often safer to rely on scientific notation ($10^n$) to avoid this billion-trillion-septillion confusion, as the meaning of the word can shift by a factor of $10^{15}$ depending on the region.

SI Prefixes: The digital and metric equivalent

While mathematicians use terms like septillion and octillion, the scientific community and the technology sector often prefer SI (International System of Units) prefixes. These prefixes are attached to units like meters, grams, or bytes to denote magnitude.

For a long time, the highest SI prefix was "yotta-", representing $10^{24}$. Thus, one septillion bytes of data is one yottabyte.

As of late 2022, international weights and measures authorities introduced new prefixes to account for the growing volume of global data and the extreme masses of celestial bodies. These updates are essential for 2026 and beyond as we approach higher thresholds of data generation:

  • Ronna- (R): $10^{27}$ (equivalent to one octillion)
  • Quetta- (Q): $10^{30}$ (equivalent to one nonillion)

In the future, we may begin discussing "ronnagrams" to describe the mass of the Earth or "quettabytes" to quantify the storage capacity required for global AI neural networks. These prefixes provide a cleaner, more standardized way to communicate the numbers that follow sextillion without the ambiguity of the "illion" suffixes.

The Extremes: Googol and Googolplex

Beyond the standard dictionary names like decillion and vigintillion lie the "celebrity" numbers of the mathematical world. The most famous among these is the googol.

A googol is $10^{100}$, or a 1 followed by 100 zeros. Despite its fame, a googol has no practical application in counting physical objects in our universe. Astronomers estimate that there are between $10^{78}$ and $10^{82}$ atoms in the observable universe. This means a googol is trillions of times larger than the total number of atoms in existence.

Even larger is the googolplex, which is 1 followed by a googol of zeros ($10^{\text{googol}}$). Writing down a googolplex in standard decimal form is physically impossible; there is not enough matter in the universe to serve as paper and ink, nor is there enough space to fit the digits. Even if you could write 10 digits per second, it would take vastly longer than the age of the universe to finish the task.

Why we stop using names and start using notation

While it is intellectually satisfying to know that "septillion" follows "sextillion," there is a reason these names are rarely seen in peer-reviewed journals or engineering blueprints. As numbers grow, the risk of miscommunication increases.

Scientific notation ($1.0 \times 10^{24}$) is the preferred language for several reasons:

  1. Precision: It allows for the easy expression of significant figures. Writing $6.02 \times 10^{23}$ tells the reader exactly how much precision is intended, whereas writing out 24 digits can be visually overwhelming and prone to error.
  2. Calculation: Multiplying large numbers is a matter of adding exponents. For example, $(10^{21}) \times (10^{24}) = 10^{45}$. It is much simpler than trying to remember what a "sextillion" times a "septillion" equals (it's a quattuordecillion, for the curious).
  3. Universality: Scientific notation is identical in every language and every country. It bypasses the Short Scale vs. Long Scale debate entirely.

Summary of the Large Number Ladder

When someone asks what is after sextillion, they are usually looking for the next step in the ladder of magnitude. To summarize the progression in the standard American short scale:

  1. Sextillion ($10^{21}$)
  2. Septillion ($10^{24}$)
  3. Octillion ($10^{27}$)
  4. Nonillion ($10^{30}$)
  5. Decillion ($10^{33}$)

As we move further into the 21st century, these numbers are migrating from the pages of theoretical math books into practical discussions about the digital universe and quantum states. Whether you refer to it as a septillion, a yotta-unit, or $10^{24}$, you are describing a scale that encompasses the very building blocks of our reality.