# 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 170

- 170 is the smallest composite number such that exactly four distinct permutations of its decimal digits are prime (17, 71, 107, and 701 are all prime)
- 170 can be written as (2
^{2}+ 3)^{2}+ (3^{2}+ 2)^{2}) - 170 is the smallest number n, except 1, for which φ(n) and σ(n) are both square
- 170 is the smallest sphenic number (the product of three distinct primes) with no squarefree neighbors: 169 = 13
^{2}, 170 = 2 * 5 * 17, and 171 = 3^{2}* 19 (submitted by Massimo Kofler)