The value should be around 4.7kohm.
It was intended to be used with a 4.7k or 10k pull-up resistor, which will keep the current well under 3mA even if VCC is at 5.5V.
DS3231M
Production
The DS3231M is a low-cost, extremely accurate, I2C real-time clock (RTC). The device incorporates a battery input and maintains accurate timekeeping when...
Datasheet
DS3231M on Analog.com
The value should be around 4.7kohm.
It was intended to be used with a 4.7k or 10k pull-up resistor, which will keep the current well under 3mA even if VCC is at 5.5V.