diff --git a/changes/1317-samuelcolvin.md b/changes/1317-samuelcolvin.md
new file mode 100644
index 0000000..af16af0
--- /dev/null
+++ b/changes/1317-samuelcolvin.md
@@ -0,0 +1 @@
+fix card number length check in `PaymentCardNumber`, `PaymentCardBrand` now inherits from `str`.
diff --git a/pydantic/types.py b/pydantic/types.py
index 2aa4c96..b7627bb 100644
--- a/pydantic/types.py
+++ b/pydantic/types.py
@@ -591,7 +591,7 @@ class SecretBytes:
         return self._secret_value
 
 
-class PaymentCardBrand(Enum):
+class PaymentCardBrand(str, Enum):
     amex = 'American Express'
     mastercard = 'Mastercard'
     visa = 'Visa'
@@ -666,7 +666,7 @@ class PaymentCardNumber(str):
         https://en.wikipedia.org/wiki/Payment_card_number#Issuer_identification_number_(IIN)
         """
         required_length: Optional[int] = None
-        if card_number.brand is (PaymentCardBrand.visa or PaymentCardBrand.mastercard):
+        if card_number.brand in {PaymentCardBrand.visa, PaymentCardBrand.mastercard}:
             required_length = 16
             valid = len(card_number) == required_length
         elif card_number.brand is PaymentCardBrand.amex:
diff --git a/tests/test_types_payment_card_number.py b/tests/test_types_payment_card_number.py
index 28cbe15..dcf321c 100644
--- a/tests/test_types_payment_card_number.py
+++ b/tests/test_types_payment_card_number.py
@@ -78,6 +78,7 @@ def test_validate_luhn_check_digit(card_number: str, valid: bool):
         (VALID_AMEX, PaymentCardBrand.amex, True),
         (VALID_OTHER, PaymentCardBrand.other, True),
         (LEN_INVALID, PaymentCardBrand.visa, False),
+        (VALID_AMEX, PaymentCardBrand.mastercard, False),
     ],
 )
 def test_length_for_brand(card_number: str, brand: PaymentCardBrand, valid: bool):
@@ -123,3 +124,21 @@ def test_error_types(card_number: Any, error_message: str):
     with pytest.raises(ValidationError, match=error_message) as exc_info:
         PaymentCard(card_number=card_number)
     assert exc_info.value.json().startswith('[')
+
+
+def test_payment_card_brand():
+    b = PaymentCardBrand.visa
+    assert str(b) == 'Visa'
+    assert b is PaymentCardBrand.visa
+    assert b == PaymentCardBrand.visa
+    assert b in {PaymentCardBrand.visa, PaymentCardBrand.mastercard}
+
+    b = 'Visa'
+    assert b is not PaymentCardBrand.visa
+    assert b == PaymentCardBrand.visa
+    assert b in {PaymentCardBrand.visa, PaymentCardBrand.mastercard}
+
+    b = PaymentCardBrand.amex
+    assert b is not PaymentCardBrand.visa
+    assert b != PaymentCardBrand.visa
+    assert b not in {PaymentCardBrand.visa, PaymentCardBrand.mastercard}