Number Gossip
(Enter a number and I'll tell you everything you wanted to know about it but were afraid to ask.)
Unique Properties of 31
- 31 is the earliest and the only known case such that the sum of the divisors of two distinct numbers (16 & 25) is the same prime quantity (31), that is to say: 1+2+4+8+16 = 31 and 1+5+25 = 31
- 31 is the number of minimal composites which cover the set of composites in base 10
- There are only 31 numbers which cannot be expressed as the sum of distinct squares
- 31 = 22 + 33, i.e., the sum of the first two primes raised to themselves
- 31 is the smallest prime that is a sum of two triangular numbers with prime indices