Wednesday, December 24, 2014

2015

2015 = 5 x 13 x 31.

2015 is palindromic in base 2 (binary): 11111011111 (A030130 and A168355). 2015 repeats the string 133 in base 4: 133133 (A020332). It repeats the string 37 in base 8: 3737 (A020336).

2015 is a Lucas-Carmichael number (A006972 and A129868).

2014, 2015, and 2016 each have three distinct prime factors (sphenic numbers) (A168626).

2015 is the sum of 10 distinct powers of 2 (A038461).

2015 is a number that cannot be written as a sum of three squares.

2015 divides 924 - 1.


2015 is a year with exactly three "Friday the 13ths" (A190653).

2015 is a year in which a blue moon occurs (a second full month to occur in a single calendar month) (A125680).

The year 2015 is the 100th anniversary of the founding of the Mathematical Association of America.


Source: OEIS