calculator-radix-grouping-mode

calculator-radix-grouping-mode is a variable defined in `calculator.el'.
Its value is

t

Documentation:
Use digit grouping in radix output mode.
If this is set, chunks of `calculator-radix-grouping-digits' characters
will be separated by `calculator-radix-grouping-separator' when in radix
output mode is active (determined by `calculator-output-radix').

You can customize this variable.