Increasing 'max_allowed_packet'

Hi.

I am getting this error on one of my scripts:

Could not Insert to CB_MAIN (update)Got a packet bigger than 'max_allowed_packet' bytes

I guess that I need to increase the 'max_allowed_packet' byte value in MySQL

With VirtualMin there is the option to change "MySQL System Variables"

In there I find that 'max_allowed_packet' is set to : 1048576

What is a reasonable figure to increase it to ?

Also why ıs it 1048576 and not 1,000,000 ?

I am going to double the number up to 2,097,152 and see what happens !

Is there any other variable that should also be adjusted ?

Thanks