13

This number is a prime.

Just showing those entries submitted by 'Homewood': (Click here to show all)

ELEVEN PLUS TWO and TWELVE PLUS ONE both contain 13 letters. [Homewood]

In 2013 there were two 'Friday the 13ths' exactly 13 weeks apart. [Homewood]

Arsenal F.C have won the English F.A. Cup a record 13 times. They have also won 13 League titles. [Homewood]

A four-digit number abcd is divisible by 13 if 13 divides a + 4b + 3c + 12d. d is calculated using the coefficients of a + 4b + 3c which shows if a three-digit number is divisible by 13. b * c / a = 12 and a five-digit number is divisible by 13 if 13 divides a + 4b + 3c + 12d + 9e because the coefficients of c * d / b = 9. multiplying the last two coefficients and dividing by the one before them will always give the next term in this equation and therefore any number of any length can be checked for divisibility by 13. [Homewood]

All digits 1 thru 9 appear in the first 13 decimal digits of π. [Homewood]

The first sum of two squares where the two numbers are prime and the sum is also prime. (2² + 3² = 13). [Homewood]