This problem is inspired by Project Euler 520: Simbers.

"We define a simber to be a positive integer in which any odd digit, if present, occurs an odd number of times, and any even digit, if present, occurs an even number of times.

For example, 141221242 is a 9-digit simber because it has three 1's, four 2's and two 4's."

Given a number, determine if it a simber or not. Please note that the number will be in string format as some of the entries may be quite long. You can assume there will be no leading zeroes in any of the numbers.