Image from the jigsaw puzzles.
Occurrences in the show
Oceanic Flight 815 left Sydney from Gate 23.
- Jack sat in seat 23B. ("Pilot, Part 1")
- Rose sat in seat 23D. ("Pilot, Part 1")
- Bernard sat in seat 23E. ("Pilot, Part 1")
- Kate had a $23,000 bounty on her head. ("Tabula Rasa")
- Danielle asked Sayid where Alex was 23 times. ("Solitary")
- Jack pounded on Charlie's chest 23 times until Kate made him stop. ("All the Best Cowboys Have Daddy Issues")
- Drive Shaft was 234 on the juke box. ("Homecoming")
- The number 23 appeared as part of a PIN on one of the crates found inside the drug smugglers' plane. ("Deus Ex Machina")
- The departure gate for flight 815 was 23. ("Exodus, Part 1")
- Hurley's hotel room in Sydney was number 2342. ("Exodus, Part 2")
- The temperature in Sydney the day Flight 815 departed was 23°C.
- The Oceanic logo was made of 23 dots.
There were 23 survivors at the tail section of the plane.
- 23 is the second to last number to the combination in the hatch gun safe. ("Man of Science, Man of Faith")
- When Jack met Desmond in the stadium, Jack tripped when he was about to get past seat row Number 23.
- The letter "W", which prominently appears on a woman's t-shirt in the caves as Jack reassured them of their safety, is the 23rd letter of the alphabet. ("Man of Science, Man of Faith")
- 23 people survived the crash in the tail end of the plane according to Libby (this, however, included Goodwin). ("Everybody Hates Hugo")
- There were 23 survivors outside of the mid-section 42: the 22 tailies and the pilot. ("The Other 48 Days")
- Nathan died on Day 23. ("The Other 48 Days")
- The timer had 23 seconds left when Jack and Locke discovered that Kate abandoned the Swan. ("What Kate Did")
- Eko recited Psalm 23 as he set the plane on fire. The 23rd Psalm is also the episode title. ("The 23rd Psalm")
- Part of the video reel that Kelvin showed to Sayid was number 23108-42 . ("One of Them")
- Sayid said he was 23 years old when he was captured in the Persian Gulf War. ("One of Them")
- The sum of the real Henry Gale's zip code numbers was 23. ("One of Them")
- 23 people were standing on the deck when it collapsed with Hurley on it; Dr. Brooks said it was built to only hold 8. ("Dave")
- Desmond looked at letters he sent to Penny while he was in jail. Penny's address was 23 Dansmore Gardens. ("Live Together, Die Alone, Part 1")
- The number 23 was on one of the LAPD cars. ("Two for the Road")
Karl inside Room 23.
- Jack's pager had the time 7:15:23 on it. ("A Tale of Two Cities")
- Eddie Colburn's Humboldt County Sheriff's Department ID number was 84023. ("Further Instructions")
- Munson's 10 Million was hidden in unit 23c. ("Every Man for Himself")
- Eko was reciting the 23rd Psalm when the Monster attacked him. ("The Cost of Living").
- Karl was being held in room 23 in the Hydra prison. ("Not in Portland")
- Juliet entered 1623 into the sonic fence keypad. ("Left Behind")
- The radio volume in the van was set to level 23 when Drive Shaft's song started playing. ("Greatest Hits")
Channel 23 plays Drive Shaft.
- The docket number of Kate's trial was 42231615, the last four Numbers in reverse. ("Eggtown")
- The appropriate setting for Daniel Faraday's consciousness time-transporting device at Oxford University's Queen's College Physics Department was 2.342. ("The Constant")
- The journal of the first mate of the Black Rock was sold at auction in lot #2342. ("The Constant")
- Penelope Widmore's home address was 423 Cheyne Walk. ("The Constant")
- There were written "X"s marking every day from October 1st to December 23rd on the 2004 calendar in the freighter's sickbay. In addition, only four of these "X"s were marked in yellow on the days of October 20th through October 23rd. ("The Constant")
- The license plate number of the taxi Jin chased was 2369. ("Ji Yeon")
- The secret clues on yahoo's web site http://au.yahoo.com/lost/clue/clue407.html mentions that the last Year of the Dragon ("Ji Yeon") is from the 5th of February 2000 to the 23rd of January 2001
- In the episode Confirmed Dead, there was a bucket or something metallic with the number 23 on it during the sub team excavation.
- Jack's cell phone number was 323-555-0156. ("The Lie")
- Ben instructed Jack to meet up at the Long Beach Marina, Slip 23. ("The Little Prince")
- The photo of the island that Jack saw in the Lamp Post station was dated 9/23/54. The sum of these digits equals 23: 9+2+3+5+4. ("316")
- As Eloise Hawking was explaining the origins of the Lamp Post to everyone, the camera sweeps over the floor, and scribbled on the map of the Pacific are several numbers — including 30' 23 N, and 15' 22 E. ("316")
- Widmore instructed Locke to dial 23 whenever Locke needed to get in contact with him on the international phone that he gave him. ("The Life and Death of Jeremy Bentham")
- Richard first met Daniel in 1954 and again 23 years later in 1977. ("Jughead") ("The Variable")
- Sayid assassinated a man at the address 23 […Russian text]. ("He's Our You")
- On the Sports Illustrated that Miles reads in Some Like It Hoth, it reads "After 23 years…"
Jack is revealed to be number 23 inside Jacob's cave wall in "The Substitute".
- The numbers in the license plate (4DQ5554) of the taxi that Kate carjacked add up to 23. ("What Kate Does")
- The finale of the series aired on Sunday, May 23, 2010.
- Jack Shephard was number 23 on Jacob's list on the cave wall. ("The Substitute")
- When the lens assembly at the top of the Lighthouse was aligned to 23 degrees, Jack Shephard's childhood home could be observed. ("Lighthouse")
- The numerical address for the home of David Shepard's mother was 23.
- When Sayid was woken up by Omer in the flash-sideways, he commented that it was 2:30 in the morning. ("Sundown")
- When Lapidus was lifting off the Ajira plane, the odometer spun past 23 then 42. ("The End")
- At the concert, Jack's family sat at table 23. ("The End")
- The Apollo bar Sawyer bought at the hospital was on slot 23 of the candy machine. ("The End")
The Lost Experience
- There were 23 minutes between Zander and Cliff's births. (Bad Twin)
- The Hanso Foundation wished to purchase 23 Jeep Compass vehicles. (DaimlerChrysler Fleet Operations)
Outside the show and real life occurrences
- The 23rd Psalm starts "The Lord is my Shepherd," which is also the number given to Jack Shephard. 
- In the Bible 23 is the number of letters in the verse "And God said, ‘Let there be light!’ And there was light." || ויאמר א-להים יהי אור ויהי אור – Genesis 1:3.
- Building 23 is the name of the building in Burbank, CA where Lost executive producer Damon Lindelof works.
- 23-skidoo (sometimes spelled 23-skiddoo) was an American slang phrase in the early 20th century meaning, "Let's get out of here as fast as we can!"
- 23 is said to be the number of the Illuminati and as such has part in many conspiracy theories. One of the most notable examples is Robert Anton Wilson and Robert Shea's novel, The Illuminatus! Trilogy, in which the repeated occurrences of the number 23 in seemingly disparate situations is a principal plot element. There have been a few quotes from Damon Lindelof in interviews, pertaining to Illuminatus! and its influence on Lost.
- The Principia Discordia, principle text of the Discordian religion, holds high regard for "The Holy 23," due to its relation to the number 5. The Law of Fives states that "All things happen in fives, or are divisible by or are multiples of five, or are somehow directly or indirectly appropriate to 5. The Law of Fives is never wrong." The Principia and its constituent ideas were a strong influence on Robert Anton Wilson, among others.
- Humans have 23 pairs of chromosomes.
- There are 23 discs in the human spine, Jack is a spinal surgeon.
- The Earth's axis is tilted at a 23.5 degree angle.
- Latitude 4.815, Longitude 162.342 are the GPS coordinates that lead to a point in the Pacific Ocean on the trail from Australia to L.A. If you go to these coordinates in Google Maps , there is a real island very close to those coordinates. On that island there is a runway marked 23, and another runway marked 5.
- The average person breathes about 23,000 times a day.
- In the sci-fi TV series Max Headroom, the heroes worked for TV station Network 23.
- It takes 23 seconds for blood to make a complete circuit of the human body.
- Michael Jordan and his famous jersey 23.
- Lebron James and his famous jersey 23.
- There are 23 steps between floors in the Pentagon.
- Julius Caesar was stabbed 23 times.
- Laura Palmer was killed on Feb. 23.
- The Number 23 is a movie starring Jim Carrey. It was released on Feb. 23, 2007.