# 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 […]

# 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 […]

# What’s Next?: An Unorthodox Number Sequence

0, 0, 0, 0, 4, 9, 5, 1, 1, 0, 55, 55, 1, 0, 1, 9, ? What is the next number in the sequence?

# 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 […]

# 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 […]

# 1-2-3-4 Puzzle

Using the digits 1, 2, 3, 4 twice, form an eight-digit number in such a way that there is one digit between the 1’s, two digits between the 2’s, three digits between the 3’s and four digits between the 4’s.

# Different Mathematical Perspectives

Here is a very simple match puzzle. Move just a single match to form a perfect square. This is indeed an easy puzzle. However, there are two ways to solve this and the solution depends on who’s solving the puzzle.

# A Curious Clock Puzzle

Draw two straight lines across the face of the clock in such a way so that the sum of the numbers in every section are the same.