55

55 = 5 x 11.

55 is the tenth Fibonacci number.

55 is the tenth triangular number.

55 is a pyramidal number, the sum of the first five square numbers: 55 = 1² + 2² + 3² + 4² + 5².

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

An emerald anniversary celebrates 55 years.

Source: Phillips, R. 2004. Numbers: Facts, Figures and Fiction. Badsey Publications.

140

140 = 2² x 5 x 7.

140 has a unique representation as a sum of three squares: 140 = 2² + 6² + 10².

140 is a square pyramidal number. It is the sum of the first seven squares: 140 = 1² + 2² + 3² + 4² + 5² + 6² + 7².

140 is a harmonic divisor number.

140 Siwa is a large, dark asteroid discovered in 1874.

Source: Prime Curios!

506

506 = 2 x 11 x 23.

506 is a pronic number because it is the product of two consecutive integers: 22 x 23 = 506.

506 is the sum of the first eleven squares: 1² + 2² + . . . + 10² + 11² = 506 (which makes it a square pyramidal number).

506 is a hendecagonal number.

The telephone area code 506 covers the Canadian province of New Brunswick.

Source: Number Gossip

650

650 = 2 x 5² x 13.

650 is a pronic number. It is the product of two consecutive integers: 25 x 26 = 650.

650 is the sum of the first 12 squares. Hence, it is a pyramidal number.

650 is 22022 in base 4 and 1616 in base 7.


In the 1950s, advanced features of the IBM 650 Magnetic Drum Data Processing Machine brought increased reliability to the young field of electronic computing.

Source: Number Gossip

30

30 = 2 x 3 x 5.

30 is the smallest number with three distinct prime divisors.

30 has a unique representation as a sum of three squares: 30 = 1² + 2² + 5².

30 is a pyramidal number (the sum of all squares of integers from 1 to 4): 30 = 1² + 2² + 3² + 4².

30 is 33 in base 9.

A dodecahedron is a Platonic solid with 30 edges.


Source: Number Gossip