Muhammed is a false prophet, because Christ said the prophets after His time will be sent in His name:
"Therefore I AM SENDING YOU PROPHETS AND WISE MEN AND TEACHERS. Some of them you will kill and crucify; others you will flog in your synagogues and pursue from town to town." - Matthew 23:34
As we all know, Muhammed did not come in the name of Jesus Christ, therefore he is a false prophet. He could not have come in the name of the Father, because the Bible itself says Christ is the seal (not Muhammed) of the ones He would send.
Daniel 9:20-26>While I was speaking and praying, confessing my sin and the sin of my people Israel and making my request to the LORD my God for his holy hill - while I was still in prayer, Gabriel, the man I had seen in the earlier vision, came to me in swift flight about the time of the evening sacrifice. He instructed me and said to me, 'Daniel, I have now come to give you insight and understanding. As soon as you began to pray, an answer was given, which I have come to tell you, for you are highly esteemed. Therefore, consider the message and understand the vision: 'Seventy "sevens" are decreed for your people and your holy city to FINISH transgression, to put an end to sin, to atone for wickedness, to bring in everlasting righteousness, TO SEAL UP VISION AND PROPHECY and to anoint the most holy. Know and understand this: From the issuing of the decree to restore and rebuild Jerusalem until the Anointed One (Messiah), the ruler, comes, there will be seven "sevens," and sixty-two "sevens." It will be rebuilt with streets and a trench, but in times of trouble. After the sixty-two "sevens," the Anointed One (Messiah) will be CUT OFF and will have nothing. The people of the ruler who will come will destroy the city and the sanctuary. The end will come like a flood: War will continue until the end, and desolations have been decreed.
John 6:27>Do not work for food that spoils, but for food that endures to eternal life, which the Son of Man will give you. On him God the Father has placed HIS SEAL OF APPROVAL.
Also, notice the parable given by Jesus in Mark 12:1-8 about the vineyard. The planter lent the yard to husbandmen, and at times the planter would send servants to check on the yard which the husbandmen were to take care of. Everytime the planter sent servants, the husband men would kill them (referring to Israel killing the prophets). Then notice what Jesus says in verse 6: Having yet therefore one son, his wellbeloved, he sent him also last unto them, saying, They will reverence my son.
So Muhammed can't be the last prophet sent by the Father, and Muhammed can't be a prophet because he did not come in the name of Christ.
The LORD's Word has already spoken. Amen.