If by "splitting up", you mean creating a new layer per unique attribute value, there is the tool 'Split vector layer'. It will do what you need withwithout having to convert the date field. However, you should consider whether creating 254 layers is really appropriate.
If you want the date as an integer without the seconds displayed, you can use an expression like this on your DateTime field:
to_int(format_date("datetime", 'yyyyMMddHHmm'))
See the help panel of the Field Calculator for explanation of the format notation.
Example output:
16/10/2022 17:14:23 ---> 202210161714