393 = 3 x 131.
1000393 - 393 is a prime number. It is the second and largest known number with this property.
393 is 12021 in base 4. It is 3033 in base 5 and 1101 in base 7.
393 is a number n such that n, n + 1, and n + 2 are each products of two primes: 394 = 2 x 197 and 395 = 5 x 79.
Source: Prime Curios!