How Many Zeros in a Undecillion?
An undecillion has 36 zeros: 1,000,000,000,000,000,000,000,000,000,000,000,000. In scientific notation, the zeros in an undecillion are represented as 1036. Undecillion is the 12th named power of one thousand in the short-scale system used in the United States and United Kingdom. The prefix undec- combines un- (one) and dec- (ten), indicating the eleventh group of three zeros beyond the ones place. In the long-scale system used in parts of continental Europe, an undecillion instead has 66 zeros (1066) — a dramatically different quantity that shares only its name with the short-scale version. Learn more about centillion zeros.
A undecillion has
36
zeros
- Written Form
- 1 followed by 36 zeros
- Scientific
- 10³⁶
How Many Zeros Are in Undecillion — Short Scale vs Long Scale?
The number of zeros in an undecillion depends entirely on which numbering convention you are using. The two systems diverge significantly at this level:
| System | Zeros | Scientific Notation |
|---|---|---|
| Short scale (US / modern UK) | 36 | 1036 |
| Long scale (continental Europe) | 66 | 1066 |
The gap of 30 zeros between the two systems means the long-scale undecillion is a nonillion times larger than the short-scale one. This is the same fundamental split that affects all the large "-illion" names — the long scale assigns each new name a million times the previous, while the short scale uses a factor of one thousand. Learn more about how many zeros does a trillion have.
For all modern English-language purposes — science, finance, education — undecillion means 36 zeros and 1036. This is the definition used by dictionaries, textbooks, and scientific institutions in the US and UK.
How Many Zeros Separate Undecillion from Its Neighbors?
In the short-scale sequence, undecillion sits between decillion (1033) and duodecillion (1039), each step adding three zeros:
| Name | Zeros | Scientific Notation |
|---|---|---|
| Decillion | 33 | 1033 |
| Undecillion | 36 | 1036 |
| Duodecillion | 39 | 1039 |
Numbers at the undecillion scale and beyond appear almost exclusively in theoretical contexts — quantum physics calculations, combinatorics, and cosmological estimates. The observable universe contains roughly 1080 atoms, so an undecillion (1036) still falls well short of that count, sitting about 44 orders of magnitude below it. Learn more about septillion zeros.