How big can be the smallest prime factor of a composite integer?
Theorem 2. If n is a composite integer, then n has a prime divisor less
If n is composite, then n=ab for some integers a,b greater than 1.
We must have a??n or b??n, since otherwise ab > ?n * ?n = n.
Thus, n has a positive divisor not exceeding ?n.
prime or (by the Fundamental Theorem of Arithmetic) has a prime
In either case, n has a prime divisor not exceeding ?n.
--- Yes, because it is not divisible by 2, 3, 5 or 7.