Prime numbers within 20 are multiples within 100
Except 1, they are all multiples of! 2 (50): multiples of 2, 4, 6,..., 1003 (33): multiples of 3, 6, 9,..., 995 (20): multiples of 5, 10, 15,..., 1007 (14): multiples of 7, 14, 21,..., 9811 (9): multiples of 11, 22, 33,..., 9913 (7
The sum of all prime numbers within 20
2+3+5+7+11+13+17+19=77
How many primes are there within 20
2 3 5 7 11 13 17 19
Eight in all