Numeric literals cannot contain dollar signs or commas, but they can be written in scientific notation.
declare
v_real1_nr NUMBER:=$123456.00; -- INVALID
v_real2_nr NUMBER:=123,456.00; -- INVALID
v_real3_nr NUMBER:=5e10; -- VALID
v_real3_nr NUMBER:=5e-3; -- VALID
begin
...
Oracle supports scientific notation for numbers between 1.0 * 10^?130 and 1.0 * 10^126.
Or between 1E-130 and 1E * 126, where E stands for "times ten to the power of."