diff --git a/pkgs/racket-test-core/tests/racket/number.rktl b/pkgs/racket-test-core/tests/racket/number.rktl
index b40c48cbe7..be9bf5357a 100644
--- a/pkgs/racket-test-core/tests/racket/number.rktl
+++ b/pkgs/racket-test-core/tests/racket/number.rktl
@@ -2466,6 +2466,8 @@
 (test 0.1 string->number (string-append "0." (make-string 400 #\0) "1e400"))
 (test 0.1 string->number (string-append "0." (make-string 8000 #\0) "1e8000"))
 (test 1.0e-101 string->number (string-append "0." (make-string 8000 #\0) "1e7900"))
+(test 1.0e-101 string->number (string-append "1/1" (make-string 8000 #\0) "1e7900"))
+(test 1.0e-101 string->number (string-append "1/1" (make-string 8000 #\0) "#e7900"))
 (test +inf.0 string->number (string-append "0." (make-string 400 #\0) "1e1000"))
 (test -inf.0 string->number (string-append "-0." (make-string 400 #\0) "1e1000"))
 (test +inf.0 string->number (string-append "0." (make-string 8000 #\0) "1e8400"))
@@ -2474,6 +2476,18 @@
 (test #t extflonum? (string->extfl-number (string-append "-0." (make-string 8000 #\0) "1t8400")))
 (test #f string->number (string-append "-0." (make-string 8000 #\0) "9e10000") 8)
 (test #f string->number (string-append "0." (make-string 8000 #\0) "e1008") 8)
+(test 1.333602886575971e+241 string->number "#b10e1100100000")
+(test 2.999393627791262e-241 string->number "#b10e-1100100000")
+(test 3.334007216439927e+240 string->number "#b1/10e1100100000")
+(test 1.0 string->number (string-append "#i1" (make-string 8000 #\0) "/" "1" (make-string 8000 #\0)))
+(test 10.0 string->number (string-append "1" (make-string 8000 #\0) "#/" "1" (make-string 8000 #\0)))
+(test 1.0 string->number (string-append "1" (make-string 8000 #\0) "#/" "1" (make-string 8000 #\0) "#"))
+(test 1.0+3.0i string->number (string-append "#i1" (make-string 8000 #\0) "/" "1" (make-string 8000 #\0) "+3.0i"))
+(test 10.0+3.0i string->number (string-append "#i1" (make-string 8000 #\0) "/" "1" (make-string 7998 #\0) "#+3.0i"))
+(test 1.0+0.0i string->number (string-append "#i1" (make-string 8000 #\0) "/" "1" (make-string 8000 #\0) "@0"))
+(test 10.0+0.0i string->number (string-append "#i1" (make-string 8000 #\0) "/" "1" (make-string 7998 #\0) "#@0"))
+(test 1 string->number (string-append "1" (make-string 8000 #\0) "/" "1" (make-string 8000 #\0) "@0"))
+(test 10.0 string->number (string-append "1" (make-string 8000 #\0) "/" "1" (make-string 7998 #\0) "#@0"))
 
 (test #t andmap (lambda (x) (and (>= x 0) (< x 10))) (map random '(10 10 10 10)))
 (test (void) random-seed 5)
diff --git a/pkgs/racket-test-core/tests/racket/numstrs.rktl b/pkgs/racket-test-core/tests/racket/numstrs.rktl
index b6e0edaf6c..e42146959a 100644
--- a/pkgs/racket-test-core/tests/racket/numstrs.rktl
+++ b/pkgs/racket-test-core/tests/racket/numstrs.rktl
@@ -120,6 +120,8 @@
     (-inf.0 "-1/0#")
     (DBZ "1#/0")
     (DBZ "-1#/0")
+    (+inf.0 "#i1#/0")
+    (-inf.0 "#i-1#/0")
     (NOE "#e+inf.0")
     (NOE "#e-inf.0")
     (NOE "#e+nan.0")
diff --git a/pkgs/racket-test-core/tests/racket/read.rktl b/pkgs/racket-test-core/tests/racket/read.rktl
index d36bbb8b29..fc93fc2999 100644
--- a/pkgs/racket-test-core/tests/racket/read.rktl
+++ b/pkgs/racket-test-core/tests/racket/read.rktl
@@ -110,6 +110,23 @@
   (err/rt-test (readstr "#fals")  exn:fail:read:eof?)
   (err/rt-test (readstr "#falser") exn:fail:read?))
 
+(parameterize ([read-decimal-as-inexact #f])
+  (test 1 readstr "1.0")
+  (test 100000 readstr "1e5")
+  (test 100000 readstr "1#e4")
+  (test 10 readstr "1#")
+  (test 1/2 readstr "1#/20")
+  (test 1/2 readstr "10/2#")
+  (test 1/2 readstr "1#/2#")
+  (test 1/2 string->number "1#/2#")
+  (test 10+3i readstr "1#+3i")
+  (test 1+30i readstr "1+3#i")
+  (err/rt-test (readstr "1#/0") exn:fail:read?)
+  (err/rt-test (readstr "1/0#") exn:fail:read?)
+  (err/rt-test (readstr "1#/0#") exn:fail:read?)
+  (test #f string->number "1#/0")
+  (test #f string->number "1/0#"))
+
 (test (integer->char 0) readstr "#\\nul")
 (test (integer->char 0) readstr "#\\Nul")
 (test (integer->char 0) readstr "#\\NuL")
diff --git a/racket/src/expander/read/number.rkt b/racket/src/expander/read/number.rkt
index acba278d09..98c2ded502 100644
--- a/racket/src/expander/read/number.rkt
+++ b/racket/src/expander/read/number.rkt
@@ -488,7 +488,10 @@
        [(and (eq? convert-mode 'number-or-false) get-extfl?)
         #f]
        [(and (or (eq? exactness 'inexact) (eq? exactness 'decimal-as-inexact))
-             ((abs e-v) . > . (if get-extfl? 6000 400)))
+             (let ([m-v-e (/ (- (integer-length (numerator m-v))
+                                (integer-length (denominator m-v)))
+                             (log radix 2))])
+               ((abs (+ e-v m-v-e)) . > . (if get-extfl? (expt 2 15) (expt 2 11)))))
         ;; Don't calculate a huge exponential to return a float:
         (real->precision-inexact
          (cond
@@ -533,9 +536,8 @@
                                       convert-mode))
      (define (get-inexact? from-pos)
        (or (eq? exactness 'inexact)
-           ;; For historical reasons, `#`s in a fraction trigger an
-           ;; inexact result, even if `exactness` is 'decimal-as-exact
-           (and (not (eq? exactness 'exact))
+           (and (not (or (eq? exactness 'exact)
+                         (eq? exactness 'decimal-as-exact)))
                 (hashes? s from-pos end))))
      (cond
        [(or (not n-v) (not d-v)) #f]
diff --git a/racket/src/racket/src/numstr.c b/racket/src/racket/src/numstr.c
index f139e66417..d3f78e7a41 100644
--- a/racket/src/racket/src/numstr.c
+++ b/racket/src/racket/src/numstr.c
@@ -357,7 +357,7 @@ static Scheme_Object *read_special_number(const mzchar *str, int pos)
 /* Exponent threshold for obvious infinity. Must be at least
    max(MAX_FAST_FLOATREAD_LEN, MAX_FLOATREAD_PRECISION_DIGITS) more
    than the larget possible FP exponent. */
-#define CHECK_INF_EXP_THRESHOLD(extfl) (extfl ? 6000 : 400)
+#define CHECK_INF_EXP_THRESHOLD(extfl) (extfl ? 32768 : 2048)
 
 /* Don't bother reading more than the following number of digits in a
    floating-point mantissa: */
@@ -1552,11 +1552,11 @@ Scheme_Object *scheme_read_number(const mzchar *str, intptr_t len,
 	/* 0.0 => -0.0 */
 #ifdef MZ_USE_SINGLE_FLOATS
 	if (SCHEME_FLTP(n)) {
-	  n = scheme_make_float(-SCHEME_FLT_VAL(n));
+          n = scheme_nzerof;
 	}
 #endif
         if (SCHEME_DBLP(n)) {
-	  n = scheme_make_double(-SCHEME_DBL_VAL(n));
+	  n = scheme_nzerod;
         }
       }
     }
diff --git a/racket/src/racket/src/startup.inc b/racket/src/racket/src/startup.inc
index de1027c9f6..5e046df494 100644
--- a/racket/src/racket/src/startup.inc
+++ b/racket/src/racket/src/startup.inc
@@ -54846,7 +54846,13 @@ static const char *startup_source =
 "(let-values() #f)"
 "(if(if(let-values(((or-part_0)(eq? exactness_0 'inexact)))"
 "(if or-part_0 or-part_0(eq? exactness_0 'decimal-as-inexact)))"
-"(>(abs e-v_0)(if get-extfl?_0 6000 400))"
+"(let-values(((m-v-e_0)"
+"(/"
+"(-"
+"(integer-length(numerator m-v_0))"
+"(integer-length(denominator m-v_0)))"
+"(log radix_0 2))))"
+"(>(abs(+ e-v_0 m-v-e_0))(if get-extfl?_0(expt 2 15)(expt 2 11))))"
 " #f)"
 "(let-values()"
 "(real->precision-inexact_0"
@@ -54907,7 +54913,9 @@ static const char *startup_source =
 "(let-values(((or-part_0)(eq? exactness_0 'inexact)))"
 "(if or-part_0"
 " or-part_0"
-"(if(not(eq? exactness_0 'exact))"
+"(if(not"
+"(let-values(((or-part_1)(eq? exactness_0 'exact)))"
+"(if or-part_1 or-part_1(eq? exactness_0 'decimal-as-exact))))"
 "(hashes? s_0 from-pos_0 end_0)"
 " #f)))))))"
 "(if(let-values(((or-part_0)(not n-v_0)))(if or-part_0 or-part_0(not d-v_0)))"