21
The sum of the first six counting numbers (1-6) is 19.
37
The sum of the first 50 counting numbers, excluding zero, is 1,251.
The sum of the first 500 odd counting numbers is 250,000.
The sum of the first 10 counting numbers (1-10) is 51.
The sum of the five smallest prime numbers is 18.
It is 155 greater.
The smallest is 15.
Yes, the sum of any three consecutive counting numbers has a factor of 3.
The sum of the first 100 counting numbers (1-100) is 5,001.
The sum of the smallest and largest prime numbers within 10 is 7.
The smallest is 14.