863

863 is a prime number.

863 is the largest three-digit prime that can be written as the sum of fifteen consecutive primes: 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71 + 73 + 79 + 83 + 89 = 863.

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

863 = (11 + 71) + (11 x 71), where 11, 71, and 863 are all primes.

863 is a value of n so that n(n + 6) is a palindrome: 863(869) = 749947.

863 is a telephone area code for central Florida.

Source: Prime Curios!

372

372 = 2² x 3 x 31.

372 has a unique representation as a sum of three squares: 372 = 4² + 10² + 16².

372 is a hexagonal pyramidal number, having the form n(n + 1)(4n - 1)/6 for n = 8.

372/(3 + 7 + 2) is a prime number, 31.

101,556 = 273 x 372 = 651 x 156.

NGC 372 is a triple star in the constellation Pisces.

Source: Prime Curios!

446

446 = 2 x 223.

446 is the smallest number that can be written as the sum of three distinct squares in eight different ways: 446 = 21² + 2² + 1² = 19² + 9² + 2² = 19² + 7² + 6² = 18² + 11² + 1² = 17² + 11² + 6² = 15² + 14² + 5² = 15² + 11² + 10² = 14² + 13² + 9².

446 is 676 in base 8 and 545 in base 9.

446 is a self number. A self number is an integer that cannot be generated by any other integer added to that other integer's digits.

446 Aeternitas is an asteroid discovered in 1899.

Source: What's Special About This Number?

655

655 = 5 x 131.

655 is a semiprime (product of two prime numbers) that is the product of two Sophie Germain primes, 5 and 131.

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

655 is a divisor of 61⁵ - 1.

655 is 22033 in base 4 and 10110 in base 5.

Iran Air Flight 655 was an airliner shot down by U.S. missiles in 1988 toward the end of the Iran-Iraq war.

Source: On-Line Encyclopedia of Integer Sequences

223

223 is a prime number.

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

223 is the smallest prime with three prime digits. The sum of the digits of first primes up to 223 is 449.

223 is the smallest prime whose reversal has more than two prime divisors: 322 = 2 x 7 x 23.

223 is the final chapter of Mark Haddon's novel The Curious Incident of the Dog in the Night-Time, which uses just prime numbers for its chapters.

Source: Number Gossip

642

642 = 2 x 3 x 107.

642 is a sphenic number because it the product of three distinct primes.

642 is the smallest number with the property that its first six multiples contain the digit 2: 642, 1284, 1926, 2568, 3210, 3852.

642 is 22002 in base 4, 1202 in base 8, and 456 in base 12.

642 Clara is an asteroid orbiting the Sun.

Source: What's Special About This Number?

426

426 = 2 x 3 x 71.

As the product of three distinct primes, 426 is known as a sphenic number.

426 is a stella octangula number. The stella octangula is a stellation of the octahedron.

426 is a number such that 10⁴²⁶ + 3 is a prime.

426 is a multiple of 6 that contains 6 in its decimal representation.

In the 1979 movie Alien, the spaceship Nostromo goes to the desolate planetoid LV-426.

Source: What's Special About This Number?