That would depend on yields. Also simply killing all humans would take much much less.
Russia has over 55000 nuclear warheads. Massive production occurred mainly after the 9/11 attack on U.S. soil. Many believe it to be in preparation for a 3rd World War.
100-140 warheads of 5 kilotons to 250 kilotons
If there are just enough nuclear weapons so yes they can destroy the World.
Which one? There are many atomic bombs and nuclear warheads that were built throughout time.
India has 85-100 nuclear warheads, around 15-20% of them aren't active.
About 30,000.
There hasn't been a test on that yet, it would also depend on how big the warheads carried were.
over 9000
In the late 1980s it peaked at somewhere over 20,000 warheads. As of 2012 the total has declined to roughly 10,000 warheads.
Destroy its cache of nuclear warheads
No one knows, but more than 100,000 were built, and we know that US & Russia admit to 28,800.
In theory, you can't destroy something and then destroy it again...
Soon after World War 2 rockets were used to carry nuclear warheads. In the space program they are used to carry many kinds of objects into space. But, they are still used to carry nuclear warheads too.
who made warheads
300
The UK is estimated to have a stockpile of approximately 160 active nuclear warheads and 225 nuclear warheads in total.
as per today's update Russia has more than 3000 nuclear warheads(deactivated),1200 warheads ready for use. US has nearly 2400 nuclear warheads stockpiled and 400 nukes ready for use.