Satan has created a network of the deceived and his deceivers. In order to deceive the entire world, he has to have many in his army for him to succeed. The first volunteers in his kingdom were the angels that followed him.
Revelation 12:7-9 And there was war in heaven, Michael and his angels waging war with the dragon. The dragon and his angels waged war, and they were not strong enough, and there was no longer a place found for them in heaven. And the great dragon was thrown down, the serpent of old who is called the devil and Satan, who deceives the whole world; he was thrown down to the earth, and his angels were thrown down with him.
Just how many angels followed him is not known, but it was a very large following.
Rev 12:3-4a Then another sign appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems. And his tail *swept away a third of the stars of heaven and threw them to the earth.
There is never given an exact count of the number of angels in heaven but it appears to be a very large, innumerable number.
Daniel 7:9-10 "I kept looking Until thrones were set up, And the Ancient of Days took His seat; His vesture was like white snow And the hair of His head like pure wool. His throne was ablaze with flames, Its wheels were a burning fire. "A river of fire was flowing And coming out from before Him; Thousands upon thousands were attending Him, And myriads upon myriads were standing before Him; The court sat, And the books were opened.
Revelation 5:11-13 Then I looked, and I heard the voice of many angels around the throne and the living creatures and the elders; and the number of them was myriads of myriads, and thousands of thousands, saying with a loud voice, "Worthy is the Lamb that was slain to receive power and riches and wisdom and might and honor and glory and blessing." And every created thing which is in heaven and on the earth and under the earth and on the sea, and all things in them, I heard saying, "To Him who sits on the throne, and to the Lamb, be blessing and honor and glory and dominion forever and ever."
Since the Greek language at the time did not include millions or billions, we are left with myriads of myriads and thousands of thousands. We can only surmise that this is a very large number, perhaps in the hundreds of millions. Regardless, Satan has a very large kingdom of fallen angels and demons to torment, destroy, and deceive. His kingdom covers the entire world.
However, he is not unrestrained in his evil intentions. He is still under the control of a sovereign, almighty, eternal God.