BigNum:format(type,precision)

Return a string representation of the BigNum value. The type argument can be one of 'e', 'g', or 'x'

e       Use scientific format, example: 1.2345678901234e18
g      Use fixed format, example: 123456789.012345
x      Use hexadecimal format, example: 0x1.2d687e3df217cec28a18p+20

The precision argument determines the maximum number of characters which will be used to output the number.