Primes That Do Not Generate Primes When Any Single Digit Is Prepended

Giving a quick inspection at the list of prime numbers, you’d notice that 2 is the first prime number. However, prepending any single decimal digit to it would not produce other primes, that is, 12, 22, 32, 42, 52, 62, 72, 82 and 92 are composite numbers. Likewise, the third prime number, 5, also shares […]

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Removing The Cherry In The Cocktail Glass: A Match Puzzle

Here is a creative match puzzle by Martin Gardner. Suppose that the four matches in the illustration above represent a cocktail glass. The objective of this puzzle is to remove the cherry from inside the glass without touching it. Also, you can only change the positions of two of the matches. The glass can either end […]

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A Little Riddle

Here’s a little riddle from Don Lemon, Everybody’s Illustrated Book of Puzzles, 1890: Twice six are eight of us, Six are but three of us, Nine are but four of us, What can we possibly be? Would you know more of us? I’ll tell you more of us. Twelve are but six of us, Five are but […]

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Full Circle

Place 24 pigs in these sties so that, no matter how many times one circles the sties, he always find that the number in each sty is closer to 10 than the number in the previous one.

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The First Odd Number In The Dictionary

Suppose that each number from 1 to 10,000,000,000 written in English and then alphabetically arranged (as in a dictionary) while ignoring spaces and hyphens. What would be the first odd number in the list?

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Curious Number Substrings

If you add all the substrings of 891, the sum is 198, which is the reverse of 891: 891 → 8 + 9 + 1 + 89 + 91 = 198 This is the only 3-digit number that has this property. There is also one 4-digit number with the same property. Can you find this […]

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Introducing Raymond Smullyan

One day, when a speaker was introducing logician and puzzlist Raymond Smullyan, he remarked that “Professor Smullyan is unique.” Smullyan, who was feeling playful that day, said, “I’m sorry to interrupt you Sir but I happen to be the only one in the entire universe who is not unique.” On another event, Smullyan was introduced […]

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A Riddle From Isaac Newton?

Horace Walpole (1717-1797) sent the following riddle to Lady Ossory, claiming that it was composed by physicist and mathematician Isaac Newton: Four people sat down at a table to play; They play’d all that night, and some part of next day; This one thing observ’d, that when all were seated, Nobody play’d with them, and […]

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Another Poem With A Hidden Acrostic

In the September 29, 1888, edition of Weekly Wisconsin, the following strange enigma appeared, composed by an anonymous writer named “Maude”: Perhaps the solvers are inclined to hiss, Curling their nose up at a con* like this. Like some much abler posers I would try A rare, uncommon puzzle to supply. A curious acrostic here […]

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