How many countries are considered to be nuclear-weapon states under the The Nuclear Threat Initiative (NPT)?

The five nuclear weapon states are China, France, Russia, the United Kingdom, and the United States.\nNPT – The Nuclear Threat Initiative\nThe NPT defines a nuclear-weapon state as a state that manufactured and exploded a nuclear weapon or other nuclear device prior to 1 January, 1967. These states are China, France, Russia, the United Kingdom, and the United States. All other states are non-nuclear-weapon states under the Treaty.\nOther states that possess nuclear weapons are India, Pakistan, and North Korea. Since the NPT entered into force in 1970, these three states were not parties to the Treaty and have conducted overt nuclear tests. North Korea had been a party to the NPT but withdrew in 2003.