The first, smallest, and only odd prime gap is 1 between the only even prime number, 2, and the first odd prime, 3. All other prime gaps are even. There is only one pair of gaps between three consecutive odd natural numbers for which all are prime. These gaps are g2 and g3 between the primes 3, 5, and 7.
Girls usually start their periods between the ages of 10 and 16. Most girls start when they're around 12. As everyone develops at different rates, there's no right or wrong age for a girl to start. Your periods will start when your body is ready, and there's nothing you can do to make them start sooner or later. If you haven't started your periods by the time you're 16, visit your doctor for a check-up.
1 Women can get their first periods as early as eight and as old as 16. 2  Most usually get theirs around the age of 11 or 12. 3  Women usually get their periods about two years after they begin developing breasts. 4  You may notice a thick, white discharge in your underpants up to 6 months before getting your first period.