Closest prime number

Write a function closestPrime(n) that returns the prime number closest to the integer n.

• A prime number is a whole number greater than 1 that can be divided evenly only by 1 and by itself: 2, 3, 5, 7, 11, 13 and so on. 1 is not a prime number. "Divided evenly" means the remainder x % i is 0.
• n is an integer from -1000 to 1000000. It can be 0, 1 or negative.
• If n is prime, return n itself.
• The distance between two numbers is the absolute value of their difference. Return the prime with the smallest distance to n.
• If two primes are equally close, return the smaller one: 12 gives 11, not 13.
• For every n that is 2 or less the answer is 2.
• Return a number, do not print it.

A simple loop over the numbers around n is enough.