I'm not sure how logical this project is, but it seemed interesting to do this without looping. It was fun.

declare @b-2 bigint = 31;

declare @out varbinary(128) = 0x;

-- simple inline tally table

with cteTen as

( select N from (values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) as t(N) ),

cteNums as

( select N = 0

union all

selecttop (63) -- the 64th bit would be bigger than a bigint max value

N = row_number() over(order by (select null))

from cteTen as cte1

cross join cteTen as cte2 ),

-- the meat of the query

cteInit as

( selectcte.N

,ValThis = power(convert(decimal(20,0), 2), N)

,ValNext = power(convert(decimal(20,0), 2), N + 1)

from cteNums as cte )

select@out = @out + convert(varbinary(1), case when (@b - (floor(@b / cte.ValNext)) * cte.ValNext) >= cte.ValThis then 1 else 0 end)

from cteInit as cte

where cte.ValThis <= @b-2

order by cte.N desc;

select @out;

This is verified to work with the largest possible bigint. I did not code it with negative numbers in mind.