How can i get better range?

Hi, i have written a code that take a decimal number and convert it to binary number.
for example 14 = 1110
The problem is that i store the number in double and when i put a number bigger than this i don't have enough bits.
How can i contain a longer number in a variable? (1001010101010101111 for example)
Thanks!

If you want more than 64 bits, you'll have to use some arbitrary-length maths library, or create your own extended type.

I have the suspicion though that you save that "binary number" as a decimal... I suggest you generate a string instead.