0000000123456789

0000000123456789 is a 16-digit decimal string consisting of seven leading zeros followed by the digits 123456789. When leading zeros are ignored, the numeric value is 123,456,789. The string illustrates fixed-width formatting and is often used as an example in discussions of zero-padding and data representation.

In computing, such sequences are common in fixed-width fields in databases, file formats, and user interfaces, where numbers must occupy a consistent width. They are also used in test data to verify that software preserves leading zeros during parsing, formatting, storage, and display, and to ensure that length constraints are handled correctly.

It is not associated with a real-world identifier or payment instrument. For validation tests, it does not satisfy the Luhn check: applying the algorithm to the digits yields a total of 47, which is not a multiple of 10. Consequently, this sequence is generally not treated as a valid card number or similar identifier.

See also: zero padding, fixed-width fields, Luhn algorithm, numeric string.