It is no coincidence that the span of each brood's cycle is a prime number of years.
Especially because his age was no longer a prime number.
British Dictionary definitions for prime number
prime number
noun
1.
an integer that cannot be factorized into other integers but is only divisible by itself or 1, such as 2, 3, 5, 7, and 11 Sometimes shortened to prime Compare composite number
prime number A positive integer greater than 1 that can only be divided by itself and 1 without leaving a remainder. Examples of prime numbers are 7, 23, and 67. Compare composite number.