diff --git a/bin/configs/kotlin-default-values-numbers.yaml b/bin/configs/kotlin-default-values-numbers.yaml
new file mode 100644
index 00000000000..1a76dd1dfde
--- /dev/null
+++ b/bin/configs/kotlin-default-values-numbers.yaml
@@ -0,0 +1,9 @@
+generatorName: kotlin
+outputDir: samples/client/petstore/kotlin-default-values-numbers
+inputSpec: modules/openapi-generator/src/test/resources/3_0/kotlin/issue13506-defaultValue-numbers.yaml
+templateDir: modules/openapi-generator/src/main/resources/kotlin-client
+additionalProperties:
+  artifactId: kotlin-default-values-numbers
+  serializationLibrary: gson
+globalProperties:
+  models: ""
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java
index a06268e50ed..fbcfed48106 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java
@@ -1001,6 +1001,20 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
         }
     }
 
+    private String fixNumberValue(String number, Schema p) {
+        if (ModelUtils.isFloatSchema(p)) {
+            return number + "f";
+        } else if (ModelUtils.isDoubleSchema(p)) {
+            if (number.contains(".")) {
+                return number;
+            }
+            return number + ".0";
+        } else if (ModelUtils.isLongSchema(p)) {
+            return number + "L";
+        }
+        return number;
+    }
+
     @Override
     public String toDefaultValue(Schema schema) {
         Schema p = ModelUtils.getReferencedSchema(this.openAPI, schema);
@@ -1014,11 +1028,11 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
             // TODO
         } else if (ModelUtils.isNumberSchema(p)) {
             if (p.getDefault() != null) {
-                return p.getDefault().toString();
+                return fixNumberValue(p.getDefault().toString(), p);
             }
         } else if (ModelUtils.isIntegerSchema(p)) {
             if (p.getDefault() != null) {
-                return p.getDefault().toString();
+                return fixNumberValue(p.getDefault().toString(), p);
             }
         } else if (ModelUtils.isURISchema(p)) {
             if (p.getDefault() != null) {
diff --git a/modules/openapi-generator/src/test/resources/3_0/kotlin/issue13506-defaultValue-numbers.yaml b/modules/openapi-generator/src/test/resources/3_0/kotlin/issue13506-defaultValue-numbers.yaml
new file mode 100644
index 00000000000..8ee94eaad2b
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/kotlin/issue13506-defaultValue-numbers.yaml
@@ -0,0 +1,51 @@
+openapi: 3.0.0
+info:
+  title: 'Issue X default value number with format'
+  version: latest
+paths:
+  '/':
+    get:
+      operationId: operation
+      responses:
+        '200':
+          description: Success
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ModelWithPropertyHavingDefault'
+components:
+  schemas:
+    ModelWithPropertyHavingDefault:
+      properties:
+        propertyInt:
+          type: integer
+          default: 0
+          format: int32
+        propertyLong:
+          type: integer
+          default: 0
+          format: int64
+        propertyFloat1:
+          type: number
+          default: 0
+          format: float
+        propertyFloat2:
+          type: number
+          default: 0.0
+          format: float
+        propertyFloat3:
+          type: number
+          default: 0.01
+          format: float
+        propertyDouble1:
+          type: number
+          default: 0
+          format: double
+        propertyDouble2:
+          type: number
+          default: 0.0
+          format: double
+        propertyDouble3:
+          type: number
+          default: 0.01
+          format: double
diff --git a/samples/client/petstore/kotlin-default-values-numbers/docs/ModelWithPropertyHavingDefault.md b/samples/client/petstore/kotlin-default-values-numbers/docs/ModelWithPropertyHavingDefault.md
new file mode 100644
index 00000000000..0d41a58b198
--- /dev/null
+++ b/samples/client/petstore/kotlin-default-values-numbers/docs/ModelWithPropertyHavingDefault.md
@@ -0,0 +1,17 @@
+
+# ModelWithPropertyHavingDefault
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**propertyInt** | **kotlin.Int** |  |  [optional]
+**propertyLong** | **kotlin.Long** |  |  [optional]
+**propertyFloat1** | **kotlin.Float** |  |  [optional]
+**propertyFloat2** | **kotlin.Float** |  |  [optional]
+**propertyFloat3** | **kotlin.Float** |  |  [optional]
+**propertyDouble1** | **kotlin.Double** |  |  [optional]
+**propertyDouble2** | **kotlin.Double** |  |  [optional]
+**propertyDouble3** | **kotlin.Double** |  |  [optional]
+
+
+
diff --git a/samples/client/petstore/kotlin-default-values-numbers/src/main/kotlin/org/openapitools/client/models/ModelWithPropertyHavingDefault.kt b/samples/client/petstore/kotlin-default-values-numbers/src/main/kotlin/org/openapitools/client/models/ModelWithPropertyHavingDefault.kt
new file mode 100644
index 00000000000..6894443aa69
--- /dev/null
+++ b/samples/client/petstore/kotlin-default-values-numbers/src/main/kotlin/org/openapitools/client/models/ModelWithPropertyHavingDefault.kt
@@ -0,0 +1,66 @@
+/**
+ * Issue X default value number with format
+ *
+ * No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)
+ *
+ * The version of the OpenAPI document: latest
+ * 
+ *
+ * Please note:
+ * This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * Do not edit this file manually.
+ */
+
+@file:Suppress(
+    "ArrayInDataClass",
+    "EnumEntryName",
+    "RemoveRedundantQualifierName",
+    "UnusedImport"
+)
+
+package org.openapitools.client.models
+
+
+import com.google.gson.annotations.SerializedName
+
+/**
+ * 
+ *
+ * @param propertyInt 
+ * @param propertyLong 
+ * @param propertyFloat1 
+ * @param propertyFloat2 
+ * @param propertyFloat3 
+ * @param propertyDouble1 
+ * @param propertyDouble2 
+ * @param propertyDouble3 
+ */
+
+data class ModelWithPropertyHavingDefault (
+
+    @SerializedName("propertyInt")
+    val propertyInt: kotlin.Int? = 0,
+
+    @SerializedName("propertyLong")
+    val propertyLong: kotlin.Long? = 0L,
+
+    @SerializedName("propertyFloat1")
+    val propertyFloat1: kotlin.Float? = 0f,
+
+    @SerializedName("propertyFloat2")
+    val propertyFloat2: kotlin.Float? = 0.0f,
+
+    @SerializedName("propertyFloat3")
+    val propertyFloat3: kotlin.Float? = 0.01f,
+
+    @SerializedName("propertyDouble1")
+    val propertyDouble1: kotlin.Double? = 0.0,
+
+    @SerializedName("propertyDouble2")
+    val propertyDouble2: kotlin.Double? = 0.0,
+
+    @SerializedName("propertyDouble3")
+    val propertyDouble3: kotlin.Double? = 0.01
+
+)
+