fun readLargeInt () =
    valOf (TextIO.scanStream (LargeInt.scan StringCvt.DEC) TextIO.stdIn)


fun canUse n =
    let
        fun canUseAux i =
            if n mod i = 0 andalso i < n then true
            else if n <= i * i then false
            else canUseAux (i + 1)
    in
        if n = 1 then false
        else canUseAux 2
    end



val () =
    let
        val n = readLargeInt ()

        val ans = if canUse n then "YES"
                  else "NO"
    in
        print (ans ^ "\n")
    end