The world will celebrate William Shakespeare's 451st birthday on Thursday -- though nobody is totally sure when exactly he was born. Historians have put the playwright's birth date at April 23 based on the date of his baptism, which in the 1500s typically took place three days after a child's birth.

One thing is for sure: From 1564 until Shakespeare's death in 1616, he was busy. The Bard wrote about 40 plays and more than 150 sonnets, earning him the title of "greatest dramatist of all time," according to Bio. His works contain more than 880,000 words, most of them in tragedies like "Romeo and Juliet" and comedies like "Much Ado About Nothing."

Want to learn more about Shakespeare? Read on for 20 interesting facts about him, compiled from No Sweat Shakespeare, the History Channel and Shakespeare-online:

1. He had four sisters -- two named Joan, one Margaret and Anne -- and three brothers -- Gilbert, Richard and Edmund.

2. People used to spell his name many different ways, including "Shakspere," "Shake-speare," "Shakespear," "Shaxberd" and "Sheakspear." 

3. He may have worn a gold earring, as depicted in the famous "Chandos" portrait of him, believed painted between 1600 and 1610. 

4. Shakespeare was probably enrolled in school until age 15. 

5. When he was 18, Shakespeare married a 26-year-old pregnant woman named Anne Hathaway.

6. They'd eventually have three children: Hamnet, Susanna and Judith. 

7. His first published play is thought to be 1594's "Henry VI, Part Two."

8. Shakespeare occasionally acted in his own plays, taking roles like the ghost in "Hamlet."

9. His shortest play is "The Comedy of Errors" at 1,770 lines; "Hamlet," with 4,042 lines, is his longest.

10. Some of his plays may have been lost or misattributed. "Double Falsehood," which was published in 1728, is thought to have been based on Shakespeare's "Cardenio."

11. In his will, Shakespeare left his wife his "second-best bed."

12. Shakespeare is to blame for the starling bird species' presence in the United States. He mentioned one in a play, and years later a man named Eugene Schieffelin released starlings into New York's Central Park so it could have all the birds referenced in Shakespeare's literature. The invasive species thrived.

13. Shakespeare introduced about 3,000 words into the English language. 

14. Among the words historians claim he invented are "frugal," "skim milk," "hint" and "bedroom."

14. There are about 13 suicides in his plays.

15. His plays have even been translated into Klingon, the language from "Star Trek."

16. The Globe Theatre is said to have stunk of garlic, beer and meat. 

17. He is buried at Holy Trinity Church in Stratford, England. He also was baptized there.

18. Shakespeare's gravestone says, "Blessed be the man that spares these stones, and cursed be he that moves my bones."

19. His cause of death is not known, though legend has it that he drank too much one night and caught a fever.

20. Two of Shakespeare's colleagues collected his plays in a text known as the First Folio after his death.