774

774 = 2 x 3² x 43.

774 is 3330 in base 6 and 1050 in base 9.

The sum of the digits of 774 is six times the number of digits: 7 + 7 + 4 = 18 = 6 x 3.

774 is the sum of twelve positive fifth powers: 744 = 3⁵ + 3⁵ + 2⁵ + 2⁵ + 2⁵ + 2⁵ + 2⁵ + 2⁵ + 2⁵ + 2⁵ + 1⁵ + 1⁵.

774 Armor is an asteroid orbiting the Sun.

Source: On-Line Encyclopedia of Integer Sequences

986

986 = 2 x 17 x 29.

986 has two representations as a sum of two squares: 986 = 5² + 31² = 19² + 25².

986 is a strobogrammatic number. It is a number that is the same whether it is viewed normally or upside down.

986 = 1⁹ + 2⁸ + 3⁶.

986 is 12421 in base 5.

NGC 986 is a galaxy in the constellation Fornax.

Source: What's Special About This Number?

803

803 = 11 x 73.

803 is the sum of three consecutive prime numbers: 803 = 263 + 269 + 271. It is also the sum of nine consecutive primes: 803 = 71 + 73 + 79 + 83 + 89 + 97 + 101 + 103 + 107.

803 is 30203 in base 4, 323 in base 16, and 203 in base 20.

803 is a divisor of 99999999.

Telephone area code 803 covers southern South Carolina.

Source: On-Line Encyclopedia of Integer Sequences

593

593 is a prime number. It is a Sophie Germain prime because 2 x 593 + 1 = 1187 is also prime.

593 has a representation as a sum of two squares: 593 = 8² + 23².

593 is the hypotenuse of a primitive Pythagorean triple: 593² = 368² + 465².

593 = 9² + 2⁹ = 3^2*2 + 2^3*3.

593 is the number on the conning tower of the submarine USS Wayne in the movie The Spy Who Loved Me.

Source: Prime Curios!

388

388 = 2² x 97.

388 has a representation as a sum of two squares: 388 = 8² + 18².

The number 388 followed by 388 sevens is a prime number.

388 is the maximum value of n so that there exist 6 denominations of stamps so that every postage from 1 to n can be paid for with at most 6 stamps.

The Junkers Ju 388 was a German World War II aircraft.

Source: Prime Curios!

531

531 = 3² x 59.

531 is the smallest number with the property that its first four multiples contain the digit 1: 531, 1062, 1593, and 2124.

291,548,736 = 8 x 92 x 531 x 746. Both the number and its factors use each of the digits from 1 to 9 exactly once.

531 is 20103 in base 4 and 213 in base 16.

The construction of the St. Sophia Basilica in Constantinople began in the year 531.

Source: What's Special About This Number?

623

623 = 7 x 89.

623 is a number that cannot be written as a sum of three squares.

623 - 6*2*3 and 623 + 6*2*3 are prime numbers: 587 and 659.

623 is the sum of three distinct positive cubes: 623 = 4³ + 6³ + 7³.

A Uranus-Neptune conjunction in Virgo occurred in the year 623.

Source: Prime Curios!

205

205 = 5 x 41.

205 has two representations as a sum of two squares: 205 = 3² + 14² = 6² + 13².

205 is the hypotenuse of two primitive Pythagorean triples: 205² = 84² + 187² = 133² + 156².

Every number greater than 205 is the sum of distinct primes of the form 6n + 1.

205 is the number of pairs of twin primes less than 10,000.

The Peugeot 205 is a supermini produced by the French car manufacturer Peugeot between 1983 and 1997.

Source: Prime Curios!

3.14159...

3.14159... (π or pi) is the ratio of a circle's circumference to its diameter.

π is the area of a unit circle. It is also the ratio of the circumference of any convex curve of constant diameter to its diameter (Barbier's theorem).

π is an irrational number and a transcendental number.

22/7 is the best approximation to π, using the ratio of two numbers less than 100.

In 1949, the ENIAC calculated π to 2037 places in 70 hours, without making any mistakes. The current record is nearly 2.7 trillion decimal digits, confirmed in January 2010.

Source: Wikipedia

535

535 = 5 x 107

5, 3, and 5 are the eighth, ninth, and tenth decimal digits of pi.

535 is a number that cannot be written as a sum of three squares.

535⁵³⁵ + (535 - 1) is a prime number.

535 is the smallest palindrome such that its cube can be written as a sum of three prime cubes: 535³ = 349³ + 379³ + 383³.

The Indonesian volcano Krakatoa erupted in the year 535.

Source: Prime Curios!

53

53 is a prime number. It is also a Sophie Germain prime because 2 x 53 + 1 = 107, which is also a prime.

5 and 3 are the eighth and ninth decimal digits of pi.

53 has a representation as a sum of two squares: 53 = 2² + 7².

53 is the hypotenuse of a primitive Pythagorean triple: 53² = 28² + 45².

53 is the sum of five consecutive primes: 5 + 7 + 11 + 13 + 17 = 53.

The chemical element iodine has atomic number 53.

Source: Prime Curios!

265

265 = 5 x 53.

2, 6, and 5 are the sixth, seventh, and eighth decimal digits of pi.

265 has two representations as a sum of two squares: 265 = 3² + 16² = 11² + 12².

265 is the hypotenuse of two primitive Pythagorean triples: 265² = 23² + 264² = 96² + 247².

265 is a centered square number.

Greek mathematician Archimedes, who is studying in Alexandria in the year 265 BC, devised a screw for raising water

Source: Wikipedia

415

415 = 5 x 83.

4, 1, and 5 are the second, third, and fourth decimal digits of pi.

415 is a number that cannot be written as a sum of three squares.

415 is the tenth Iccanobif number, where each term is the reverse of the sum of the previous two numbers.

415 is the telephone area code for San Francisco.

Source: What's Special About This Number?

852

852 = 2² x 3 x 71.

852 is a pentagonal number.

852 is the number of 6-colorable connected graphs with seven vertices.

852 is a Smith number.

NGC 852 is a galaxy in the constellation Eridanus.

Source: What's Special About This Number?

568

568 = 2³ x 71.

568 has a unique representation as a sum of three squares: 568 = 10² + 12² + 18².

568 is the smallest number whose seventh power can be written as a sum of seven seventh powers.

568 is 1441 in base 7, 161 in base 21, and 131 in base 22.

In the world of structured cabling systems, the number 568 refers to the order in which the individual wires inside a CAT 5 cable are terminated.

Source: What's Special About This Number?

375

375 = 3 x 5³.

375 is a number that cannot be written as a sum of three squares.

375 is a 5-smooth number. The product of its prime factors equals its sum of digits: 5 x 3 = 3 + 7 + 5 = 15.

Its odd powers end with 375, and its even powers end with 625.

The year 2010 is the 375th anniversary of the founding of the town of Newbury, Massachusetts.

Source: Prime Curios!

183

183 = 3 x 61.

183 is a number that cannot be written as a sum of three squares.

183 is 111 in base 13.

183 is the smallest number n so that n concatenated with n + 1 is square: 183184 = 428².

183 Istria is a stony main belt asteroid, discovered in 1878.

Source: Number Gossip

991

991 is a prime number.

991 is the largest three-digit permutable prime. In other words, 991, 919, and 199 are all primes.

991 is a number that cannot be written as a sum of three squares.

991 is the maximum number of regions into which 44 lines divide a plane.

991² = 982081 and 982 + 0 + 8 + 1 = 991.

Florida angler Allen Ogle caught a 991-pound hammerhead shark May 30, 1982.

Source: Prime Curios!