818

818 = 2 x 409.

818 is the smallest palindrome that can be expressed as the sum of the squares of two primes: 818 = 17² + 23².

818 is the only three-digit tetradic integer such that the sum of the differences of the number and each digit raised to the digit is prime: (818 - 8)⁸ + (818 - 1)¹ + (818 - 8)⁸ = 370604037770368200000817, a prime.

818 is the number of ways to dissect a 12-gon using non-crossing diagonals into polygons with an even number of sides.

818 is the telephone area code for the San Fernando Valley, California.

Source: Prime Curios!