diff --git a/libraries/stdlib/js/irRuntime/builtins/Char.kt b/libraries/stdlib/js/irRuntime/builtins/Char.kt
index 888ef6312a7..45c344c97dc 100644
--- a/libraries/stdlib/js/irRuntime/builtins/Char.kt
+++ b/libraries/stdlib/js/irRuntime/builtins/Char.kt
@@ -97,6 +97,18 @@ public inline class Char internal constructor (val value: Int) : Comparable<Char
          * The maximum value of a Unicode surrogate code unit.
          */
         public const val MAX_SURROGATE: Char = MAX_LOW_SURROGATE
+
+        /**
+         * The number of bytes used to represent a Char in a binary form.
+         */
+        @SinceKotlin("1.3")
+        public const val SIZE_BYTES: Int = 2
+
+        /**
+         * The number of bits used to represent a Char in a binary form.
+         */
+        @SinceKotlin("1.3")
+        public const val SIZE_BITS: Int = 16
     }
 
 }
\ No newline at end of file
diff --git a/libraries/stdlib/js/irRuntime/long.kt b/libraries/stdlib/js/irRuntime/long.kt
index 4ea280d3418..cd04053d84e 100644
--- a/libraries/stdlib/js/irRuntime/long.kt
+++ b/libraries/stdlib/js/irRuntime/long.kt
@@ -23,6 +23,18 @@ public class Long internal constructor(
          * A constant holding the maximum value an instance of Long can have.
          */
         public const val MAX_VALUE: Long = 9223372036854775807L
+
+        /**
+         * The number of bytes used to represent an instance of Long in a binary form.
+         */
+        @SinceKotlin("1.3")
+        public const val SIZE_BYTES: Int = 8
+
+        /**
+         * The number of bits used to represent an instance of Long in a binary form.
+         */
+        @SinceKotlin("1.3")
+        public const val SIZE_BITS: Int = 64
     }
 
     /**