+129881 5^19 + 7^13 + 23
5 raised to any power will end in 5
7^1 = 7
7^2 = 49
7^3 = 343
7^4 = 2401
7^13 ends in 7
So
5^19 + 7^13 + 23 will end in 5 + 7 + 3 = 5
The smallest prime divisor wil either be 3 or 5
[5^19 + 7^13 + 23] mod 3 = 2
[5^19 + 7613 + 23 ] mod 5 = 0
The smallest prime divisor is 5
