- The cardinal number equal to 10<sup>18</sup>.
- The cardinal number equal to 10<sup>30</sup>.
- In the English notation, the fifth power of a million, a unit followed by thirty ciphers; in the French notation, used generally in the United States, the sixth power of one thousand, a unit followed by eighteen ciphers.
- Noting a quintillion; the cardinal numeral corresponding to a quintillion: strictly a collective noun. See <internalXref urlencoded="hundred">hundred</internalXref>, a.
- A <xref>billion</xref> <xref>billion</xref>: 1 followed by eighteen zeros, 1018.
- A <xref>million</xref> <xref>quadrillion</xref>: 1 followed by 30 zeros, 1030.
- Any very large number, exceeding normal description.
- the number that is represented as a one followed by 18 zeros