how many demons or angels are there?

While it's interesting to wonder and talk about these things, I think what people who are speculating on the strength of Satan's army vs. God's are missing, is that all authority and power is given by God, even those who do evil can only do so by God-given power (Romans 13:1)
Paul may only be talking about human authority, but considering the account of Job, I think we can safely extrapolate that to include Satan and his demons.

Further to that, have you ever asked yourself if God really needs an army of angels to serve him and worship him? God, the Creator of all things, NEEDING something he created? No, he created them because he desired them, not because he needs help to fight against those he creates.

As for the so-called mystery that was mentioned, of where Cain got his wife... that has never been a mystery. The Bible doesn't name all the children of Adam and Eve, but it does say this:
(Genesis 5:3) After he begot Seth, the days of Adam were eight hundred years; and he had sons and daughters.
This is MONTHS after the fact, but I have to say this thread was an interesting read.

Here are some thoughts I have on this subject.

Angels and demons do not have freewill. Who ever said they do are wrong. Angels might have had at one point a will to choose but there is only 1 being in all of God's creation that has free will besides God, and that is us. Only Humans where made in the Image of God, meaning spirit and free will. (This is not about sovereignty vs freewill that is another discussion) ONLY humans have free will in all of creation. ALL other created things must behave in the manner that they are made.

The only other being that MIGHT have had free will is Lucifer. After which point when he rebelled he no longer had the choice. He no longer had the free will and he will for ever rebel against God. See God made certain promises to us about our free will and gifted us with that choice in the garden. Lucifer and the angels where not recipients of those gifts. And if they where that gift was revoked.

Next, why do you care about how many demons there are? there is no reason in the world a person who has been justified int he eyes of God should be afraid of Demons. They are powerless and ineffective against you. That is not to downplay what they can do, but the bible is clear, Great is he that is with in me than he that is in the world.

We as believers have the holy spirit. What the bible calls the restrainer of the sons of lawlessness. The Holy spirit is our shield, our weapon, and our terror against Demons. Mere Mortal men where able to cast out and fight against demons. Demons are chumps who wish they could get with the program. But sadly they have already lost.

And lastly there is only 1 being other than God that I fear. That is Angels. They are ones that we should be worried about. And it is good thing that we are their side. The bible describes angels as the most beautiful thing in all of creation. Even to the point of death. All recordings of human interaction with angels records that us men fell down as if we are dead, just at the mere sight of them. IN the OT the angels stroke the men who came after then when they visited Lot, with dumbness and deafness. Just be looking at them. Angels decimated Sodom and Gomorrah. Even animals are terrified of them. As seen with Balem's Donkey. An animal would rather take the beatings of her master than deal with an angel.

The bible describes Micheal as so powerful that when he comes here he has 1 foot on the land and 1 foot on the ocean. He is so powerful he is able to go Toe to Toe with Lucifer and drag him back to the throne of God for judgment. Think about that for a moment. Micheal the Archangel (NOT JESUS) is so strong and powerful that God himself does not need to deal with Lucifer. You know you are chump, when God, the maser of the universe, the all powerful being of creation, the one who holds the heavens together, doesn't even need to deal with you.

All of this is not to say, that demons aren't powerful. There are some that are very powerful. The bible says that the "Prince of Persia" The lord of the air (which may or may not be the devil himself) held up Gabriel up for days on his way to help Daniel. And even then he had to get help from Micheal. So I dont discredit them, but Angels are way more terrifying than demons. And they are on our side.