How Many Zeros in a Sextillion?
A sextillion has 21 zeros: 1,000,000,000,000,000,000,000. In scientific notation it is 1021. This is the standard short-scale definition used in the United States and modern British English — seven groups of three zeros placed after the leading 1. The prefix sex- means six, referring to the sixth group of three zeros beyond the ones place. A sextillion is one thousand times larger than a quintillion, which itself has 18 zeros, continuing the pattern where each named number in the short scale adds three more zeros to the previous one. Learn more about how many zeros in a unvigintillion.
A sextillion has
21
zeros
- Written Form
- 1 followed by 21 zeros
- Scientific
- 10²¹
How Many Zeros Are in Quintillion, Sextillion, and Septillion?
Sextillion occupies the seventh named position in the short-scale sequence (counting from million). Each step multiplies the previous value by exactly one thousand. The table below shows the three numbers immediately surrounding sextillion:
| Name | Zeros | Scientific Notation |
|---|---|---|
| Quintillion | 18 | 1018 |
| Sextillion | 21 | 1021 |
| Septillion | 24 | 1024 |
At the sextillion scale, physical quantities in science start to appear regularly. The total number of atoms in the human body is estimated at around 7 sextillion (7 × 1021). The mass of the Earth's oceans — expressed in drops of water — also reaches into the sextillion range. These are the kinds of counts where scientific notation becomes not just convenient but essentially necessary for readability. Related: How many zeros in a sexdecillion.
How Many Zeros Does a Long-Scale Sextillion Have?
In the older long-scale system — still used in some European countries and historically used in the UK before the 1970s — a sextillion represents a completely different number: 1036, or 1 followed by 36 zeros. That is an enormously larger value than the short-scale sextillion of 1021. See also: How many zeros in a quadrillion.
The long scale defines each new "-illion" as the previous one multiplied by one million rather than one thousand. So long-scale sextillion = (106)6 = 1036. By contrast, the short-scale sextillion = 103×6+3 = 1021.
This discrepancy is one reason international science and finance standardized on scientific notation decades ago. When reading historical British texts or documents from continental Europe, it is worth checking which convention the author used — the same word can differ by 15 orders of magnitude depending on context.