Numbers & Math
the School & Math shelf →
0Zero is the only number you cannot write in Roman numerals. The system simply has no symbol for it.The Roman numeral system has no symbol for zero
12,345,678,987,654,321111,111,111 multiplied by itself gives 12,345,678,987,654,321 — every digit, up the stairs and back down.Arithmetic — check it on the calculator
2,5202,520 is the smallest number that can be divided evenly by every number from 1 to 10.Arithmetic — the least common multiple of 1 through 10
4Four is the only number in English whose name has the same number of letters as the number itself.English language
40Forty is the only number whose letters, written out, are in alphabetical order.English language
153153 equals the sum of the cubes of its own digits: 1 + 125 + 27. Numbers like this are called narcissistic.Arithmetic — 1³ + 5³ + 3³ = 153
6 weeksTen factorial seconds — 10 × 9 × 8 × … × 1 seconds — is exactly six weeks. Not roughly. Exactly.Arithmetic — 10! seconds = 3,628,800 seconds
1,000In American-style number names, the letter A does not appear in any number until one thousand.English number names, American style (no "and")
7, 11, 13Take any three-digit number, repeat it (say, 472472), and the result is always divisible by 7, 11 and 13.Arithmetic — 1001 = 7 × 11 × 13
3737 × 3 is 111, 37 × 6 is 222, 37 × 9 is 333 — keep going and every multiple of three builds a triple.Arithmetic
Space
the full Weight on Other Worlds calculator →
243 daysA single day on Venus (one full spin) takes 243 Earth days — longer than a Venusian year, which takes 225.NASA — Venus planetary facts
90%On Venus you would weigh about 90% of your Earth weight. Almost like home — apart from the crushing air and acid rain.NASA — Venus surface gravity 8.87 m/s² vs Earth's 9.80
0.69 g/cm³Saturn is less dense than water. In a big enough ocean, the ringed planet would float.NASA — Saturn planetary facts
8 min 20 sThat is how old the sunlight hitting your face right now is. It left the Sun eight minutes and twenty seconds ago.Standard astronomical value — light travel time, Sun to Earth
4 KBThe Apollo 11 guidance computer had about 4 KB of RAM. Your phone is tens of thousands of times more powerful.Smithsonian / NASA — Apollo Guidance Computer specifications
93 minutesThe International Space Station circles the whole Earth about every 93 minutes — sixteen sunrises a day for the crew.NASA — International Space Station facts
88 daysA year on Mercury lasts 88 Earth days. You would have a birthday every three months.NASA — Mercury planetary facts
190+ yearsJupiter's Great Red Spot is a storm wider than Earth that has been raging, under observation, for over 190 years.NASA — Jupiter / Great Red Spot observations since 1831
1 billion tonsA single teaspoon of a neutron star would weigh about a billion tons — roughly a mountain, in a spoon.Astronomy reference estimates (NASA educational materials)
0That is the number of rainstorms that will ever wash away the footprints on the Moon. No wind, no water, no erasing.NASA — the Moon has no atmosphere and no weather
The Body
the Health & Body shelf →
100,000That is about how many times your heart beats in a single day, without you thinking about it once.American Heart Association — average heart rate arithmetic
300 → 206You are born with about 300 bones. By adulthood many have fused together, and you are down to 206.Standard anatomy references
106More than half of all your bones — 106 of 206 — live in your hands and feet.Standard anatomy references — 27 bones per hand, 26 per foot
73%Your brain is about 73% water. So is your heart. Thinking is a mostly-liquid activity.USGS — the water in your body
10,000You have roughly 10,000 taste buds, and they are replaced about every two weeks.Standard anatomy references
20,000You blink around 20,000 times a day. The whole show runs on autopilot.Ophthalmology references — 15 to 20 blinks a minute
4×Fingernails grow about four times faster than toenails. Nobody is sure why they are in such a hurry.Dermatology references
2 inchesAstronauts come back from orbit up to two inches taller. Gravity at home squeezes it back out of them.NASA — spinal decompression in weightlessness
Food
the Cooking shelf →
3,000 yearsArchaeologists have tasted honey from Egyptian tombs around 3,000 years old. It had not spoiled.Smithsonian Magazine — honey found in ancient Egyptian tombs
0That is how many botanical berries are in a punnet of strawberries. Bananas qualify. Strawberries do not.Botanical definition of a berry
25%An apple is about 25% air. That is why it floats, and part of why it crunches.Food science references — apple density
540It takes about 540 peanuts to make one 12-ounce jar of peanut butter.National Peanut Board
17th centuryThe first carrots were purple. Dutch growers bred the orange kind in the 1600s.Carrot history — Dutch breeding of orange varieties
1995The potato was the first vegetable grown in space, sprouted aboard the shuttle Columbia.NASA — potatoes grown aboard shuttle Columbia (STS-73)
1A single strand of spaghetti is called a spaghetto. One noodle, its own word.The Italian language
1834In the 1830s, ketchup was sold in the United States as medicine, in pill form.Smithsonian Magazine — Dr. John Cook Bennett's tomato pills
2The two surnames behind M&M's: Mars and Murrie. The candy is an initial each.Company history — Forrest Mars and Bruce Murrie
Games
the full Chance shelf →
300,000,000That is how many copies of Minecraft had been sold by late 2023 — the best-selling video game of all time.Microsoft / Mojang announcement (October 2023)
52!Shuffle a deck properly and the order you make has almost certainly never existed before in history.Arithmetic — 52 factorial ≈ 8 × 10⁶⁷
7On a standard die, opposite sides always add to seven: 1 faces 6, 2 faces 5, 3 faces 4.Standard die manufacture
3,333,360That is a perfect game of Pac-Man — every dot, every fruit, every ghost. First achieved in 1999.Twin Galaxies — the maximum possible Pac-Man score
1962Spacewar!, one of the very first video games, was built by MIT students on a computer the size of a car.MIT — Spacewar!, one of the first video games
10¹²⁰That is the estimated number of possible chess games — far more than the atoms in the observable universe.Claude Shannon, "Programming a Computer for Playing Chess" (1950)
1984Tetris was created in the Soviet Union by Alexey Pajitnov, on a computer with no graphics to speak of.Game history — Alexey Pajitnov, Moscow
8×A full Minecraft world is about eight times the surface area of Earth. Most players see a backyard of it.Mojang — the 60-million-block world border
1The king of hearts is the only king in the deck without a mustache.Standard English deck observation
Animals
the Pet Name Generator →
3An octopus has three hearts — and blue blood, just to show off.Standard zoology references
6 sidesWombat droppings come out as cubes. Scientists confirmed the intestine does the shaping.University research, Georgia Tech (2018–2021)
1/12 tspThat is all the honey a single bee makes in her entire life. A jar is a city's work.National Honey Board — lifetime production of one bee
2 colorsA reindeer's eyes change with the seasons — gold in summer, blue in winter — to handle Arctic light.University College London study (2013)
50 mphA mantis shrimp's punch accelerates faster than a speeding bullet and hits with that kind of speed. Aquariums keep them in thick glass.Research by Sheila Patek, UC Berkeley — mantis shrimp strike
3 yearsA snail can sleep for up to three years when the weather is wrong. Patience, perfected.Zoology references — snail hibernation and estivation
1,260A hummingbird's heart can beat up to 1,260 times a minute. Yours does about 70 and calls it a day.Smithsonian Magazine — hummingbird heart rates
400 lbsA blue whale's heart weighs about 400 pounds — roughly the size of a small golf cart.Royal Ontario Museum — blue whale heart specimen
FLAMBOYANCEThat is the official word for a group of flamingos. Somebody named them correctly.Traditional collective noun
1 best friendCows form best friendships — and measurably stress out when their best friend is taken away.Study by Krista McLennan, University of Northampton (2010)
2Humans are not the only ones with fingerprints. Koalas have them too — near-identical, even under a microscope.Discovery reported by the University of Adelaide (1996)
0That is how many of an elephant's feet ever leave the ground at once: none of them. Elephants cannot jump.Zoology references — elephant locomotion
History
the Dates & Time shelf →
229 yearsOxford University is older than the Aztec Empire — by 229 years. Students were learning there first.University of Oxford history (teaching from 1096); Tenochtitlan founded 1325
~450 yearsCleopatra lived closer in time to the invention of the iPhone than to the building of the Great Pyramid.Standard chronology — Great Pyramid c. 2560 BC, Cleopatra 69–30 BC, iPhone 2007
1700 BCWoolly mammoths were still alive around 1700 BC — centuries after the Great Pyramid was finished.Radiocarbon studies — Wrangel Island mammoths
1889Nintendo was founded in 1889. For most of its life it made playing cards, not video games.Nintendo company history
1843The first computer program was written in 1843 — by Ada Lovelace, a century before the computer existed.Ada Lovelace, Notes on the Analytical Engine
1952Albert Einstein was offered the presidency of Israel in 1952. He turned it down.Historical record — the offer of the Israeli presidency
15 cmThe Eiffel Tower grows about 15 centimeters taller in the summer heat. The iron expands; so does the tower.The Eiffel Tower official site — thermal expansion
UNICORNThat is the national animal of Scotland. It has been on the royal coat of arms for centuries.Official national animal of Scotland
38 minutesThe shortest war in history, Britain versus Zanzibar in 1896, was over in about 38 minutes.Guinness World Records — the Anglo-Zanzibar War, 1896
450 million yearsSharks were swimming the oceans tens of millions of years before the first tree ever grew.Fossil record — first sharks predate the first trees (~385 million years ago)
Money
the Money shelf →
6.6 yearsThat is the average working life of a one-dollar bill before it is worn out and replaced.Federal Reserve — average lifespan of a $1 note
3.07¢In fiscal 2023 it cost the US Mint 3.07 cents to make a coin worth one cent.US Mint Annual Report, fiscal year 2023
67,866 milesA trillion one-dollar bills stacked up would reach 67,866 miles — more than a quarter of the way to the Moon.Arithmetic — one trillion bills at 0.0043 inches thick
$10,737,418.24That is what a single penny becomes if you double it thirty times. Start small; keep doubling.Arithmetic — one cent doubled thirty times
30 mphA penny dropped from a skyscraper tops out around 30 miles an hour and flutters on the way down. It would sting, not kill.Physics references — a penny's terminal velocity