The largest integer R can hold is
.Machine$integer.max
# [1] 2147483647
This has nothing to do with scientific notation and everything to do with how the computer actually stores the numbers. The current version of R stores integers still as 32bit, regardless of the architecture. This might change in the future though.
see also ?as.integer
Currently you can get access to 64 bit integers through the int64 package
> as.integer(.Machine$integer.max)
[1] 2147483647
> # We get problems with this
> as.integer(.Machine$integer.max + 1)
[1] NA
Warning message:
NAs introduced by coercion
> # But if we use int64
> library(int64)
> as.int64(.Machine$integer.max) + 1L
[1] 2147483648