help(numeric)
sends you to help(double)
which has
Double-precision values:
All R platforms are required to work with values conforming tothe
IEC 60559 (also known as IEEE 754) standard. This basically works
with a precision of 53 bits, and represents to that precision a
range of absolute values from about 2e-308 to 2e+308. It also has
special values ‘NaN’ (many of them), plus and minus infinity and
plus and minus zero (although R acts as if these are the same).
There are also _denormal(ized)_ (or _subnormal_) numbers with
absolute values above or below the range given above but
represented to less precision.
See ‘.Machine’ for precise information on these limits. Note that
ultimately how double precision numbers are handled is down to the
CPU/FPU and compiler.
So you want to look at .Machine
which on my 64-bit box has
$double.xmin
[1] 2.22507e-308
$double.xmax
[1] 1.79769e+308
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