The Pythagoreans of ancient Greece were fascinated by whole numbers. One particular interest involved what we now call amicable numbers. Amicable numbers come in pairs in which each number is the sum ...

Primes are integers greater than 1 with only two divisors. They are the fundamental building blocks of math and the backbone of modern cryptography.

If we do not exclude unity and the number itself when summing up divisors, the 'abundant' numbers, whose divisors' sum is greater than themselves (for example, the number 18 referred to in the review) ...

For millennia, mathematicians have wondered whether odd perfect numbers exist, establishing an extraordinary list of restrictions for the hypothetical objects in the process. Insight on this question ...