Write a 6 digit whose hundred thousands digit is the greatest digit, the ones digit is the least digits and the rest of the digits are zero. How to write in figure

XXXXXX

000901

This follows your wording, but a number such as 000901 would be 901, making it a 3 digit number.

Does you number have decimals?
then how about 901.000 ?

Otherwise your question makes no sense