> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-release-file-specification/snomed-ct-identifiers/6.1-sctid-data-type.md).
# SCTID Data Type
The [SCTID](/snomed-ct-specifications/snomed-ct-release-file-specification/appendices/appendix-b.-specification-reference-information/s/sctid-data-type.md) data type is a 64-bit positive integer.
When rendered as a string an SCTID must always be represented using decimal digits and when rendered as a string has a maximum permitted length of 18 digits and a minimum length of 6 digits.
**Note** : Leading zeros are always omitted from the string rendering of an SCTID. For example the value "101291009" must not be rendered as "0101291009".
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