What column type can store txid_current value?

AFAIK txid_current returns uint 64 value (source).
However, the biggest int column type is bigint which is signed (docs).
From what I understand, NUMERIC type is slow and should be used “for storing monetary amounts and other quantities where exactness is required” (docs).

Should I store the txid_current value as text?

I need to perform mainly greater than queries on this field:

select * from t where fxid > 438298432

What would be the most efficient (from search speed POV) for full-transaction-id (unsigned integer 64)?