On average, there are as many prime numbers for which the sum of decimal digits is even as prime numbers for which it is odd. This hypothesis, first made in 1968, has recently been proven by ...

Moreover, the sum of the digits in 9-11 (9 +1+1) is 11, Sept. 11 is the 254th day of the year, the sum of 2,5, and 4 is 11, and after Sept. 11, there remain 111 days in the year.

If the sum of the digits equal 9, then the number is a multiple of 9! Back to top. Quiz: The 9 times table. Ready to put your times table knowledge to the test. Take this quiz to see how much you ...