This is the {{str number}} meta-template.

It takes a string as parameter, and returns the number of leading digits. It can count up to 25, and returns 25 if there are more.

If the parameter is empty or undefined, zero is returned:

{{str number}} returns 0
{{str number|}} returns 0
{{str number| }} returns 0

The count is interrupted by anything but the ten digits:

{{str number|abcde}} returns 0
{{str number|123456}} returns 6
{{str number|123 456}} returns 3
{{str number|1234abc}} returns 4
{{str number|1234abc56}} returns 4

If there are more than 24 leading digits, 25 is returned:

{{str number|123456789012345678901234}} returns 24
{{str number|1234567890123456789012345}} returns 25
{{str number|12345678901234567890123456}} returns 26
{{str number|123456789012345678901234a}} returns 24
{{str number|1234567890123456789012345a}} returns 25
{{str number|12345678901234567890123456a}} returns 26

The maximum is reduced if the template is called in a template parameter:

{{1x|{{str number|1234567890123456789012345}}}} returns 25

This is caused by the template depth limit (the character in a specific position of the given string is determined only if the preceding characters are all digits, hence the parser functiions are nested): if the result of finding the character in a specific position of the given string is an expansion depth error message, this message is not a digit.

Description of all string templates