Not to be confused with Ball bearing. Bearing balls are special highly spherical and smooth balls, most commonly used in ball bearings, but also used as components in things like freewheel mechanisms. The balls come in many different grades.
Euler Prime. Let a prime number generated by Euler's prime-generating polynomial be known as an Euler prime. Then the first few Euler primes occur for , 2, ..., 39, 42, 43, 45, ... (OEIS A056561), corresponding to the primes 43, 47, 53, 61, 71, 83, 97, 113, 131, 151, 173, ... (OEIS A005846).
A prime number is a number whose only proper divisor is 1. Thus a prime number can be made up only of 1's. 17 and 29 are prime numbers. Again, 1 is a proper divisor of every number (except itself), but a prime number has 1 as its only proper divisor.