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.
The average age is 12, but this does not mean that all girls start at the same age. A girl can start her period anytime between the ages of eight and 15. Usually, the first period starts about two years after breasts first start to grow. If a girl has not had her first period by age 15, or if it has been more than two to three years since breast growth started, she should see a doctor.