773

773 is a prime number.

773 has a representation as a sum of two squares: 773 = 17² + 22².

773 is the hypotenuse of a primitive Pythagorean triple: 773² = 195² + 748².

773 is the largest three-digit unholey prime; its digits have no holes.

773 is the smallest prime such that adding a preceding or trailing digit will always result in a composite if we omit the case where the leading digit is zero.

773 is a telephone area code for Chicago.

Source: Prime Curios!

1145

1145 = 5 x 229.

1145 has two representations as a sum of two squares: 1145 = 11² + 32² = 19² + 28².

1145 is the hypotenuse of two Pythagorean triples: 1145² = 423² + 1064² = 704² + 903².

1145, 1147 (31 x 37), and 1149 (3 x 383) are each semiprimes, the product of two primes.

Halley's Comet appeared in the skies in the year 1145.

Source: WolframAlpha

137

137 is a prime number.

137 has a representation as a sum of two squares: 137 = 4² + 11².

137 and 139 form a twin prime pair.

137 is the hypotenuse of a primitive Pythagorean triple: 137² = 88² + 105².

137 is a divisor of 37⁴ - 1.

137 = 128 + 8 + 1 = 2⁷ + 2³ + 2⁰.

A molecule of chlorophyll a (C₅₅H₇₂O₅N₄Mg) consists of 137 atoms.

Source: Prime Curios!

272

272 = 2⁴ x 17.

272 has a representation as a sum of two squares: 272 = 4² + 16².

272 is the number of hyperspheres in 9 dimensions that can touch an equivalent hypersphere without any intersections (Kissing Number).

272 is a pronic number, the product of two consecutive numbers: 272 = 16 x 17.

All the digits of 272 are prime, and the sum of the digits of this palindromic composite is 11, a palindromic prime. The product of the digits is 28, a perfect number.

272 is the sum of four consecutive primes: 272 = 61 + 67 + 71 + 73.

A Calorie Counter offers a list of the 272 fast food items highest in calories.

Source: Number Gossip

441

441 = 3² x 7².

441 = 21², a square.

441 is the smallest square that is the sum of six consecutive cubes: 441 = 1³ + 2³ + 3³ + 4³ + 5³ + 6³.

441 = 21² and 144 = 12². Also, 441 x 144 = 252².

441 is the telephone area code for the island of Bermuda.

Source: What's Special About This Number?

344

344 = 2³ x 43.

344 is an octahedral number.

344 is the maximum number of regions into which 19 circles divide the plane.

The sum of the squares and the sum of the cubes of the factors of 344 are both primes: 2² + 2² + 2² + 43² = 1861 and 2³ + 2³ + 2³ + 43³ = 79531.

In the year 344 B.C., the Greek philosopher Aristotle traveled from the town of Assos to the island of Lesbos to study natural history.

Source: Prime Curios!

528

528 = 2⁴ x 3 x 11.

528 is 1000010000 in base 2 (binary).

528 is the 32nd triangular number.

528 concatenated with its successor is a square: 528529 = 727².

528 is 646 in base 9.

Florida State Road 528 (SR 528) connects Orlando with Cape Canaveral.

Source: What's Special About This Number?