PYHIYP means:
Put your hands in your pockets i.e. use no calculators, no pen & paper; just your eyes and you brain.
The 1st task, a harbinger to be followed by many others, is to prove just by observation and common sense that none of the four numbers listed below is a prime.
i. 5,234,567,896,743
ii. 1,438,525,775,258,341
iii. 77,112,356,378,491
iv. 1,431,436,216,211,339
No time limit!
No cheating!
KISS!
Post your conclusions.
Inspired by Jer, I notice that
1,431,436,216,211,339 has many parts that are divisible by 13:143/13 = 11
143/13 = 11
621621/13 = ??
13/13 = 1
39/13 = 3
So if 621621 is divisible by 13, then so is the whole number.
And that is the case! 621621 = 621*1001, and 1001/13 = 77.
In hindsight, I could have used the same argument on the first 6 digits, 143143
Spoiler for iv
