This tool converts ESN (Electronic Serial Number) of cell phones from Decimal to Hexadecimal and vice-versa.
Note that this is not a normal base conversion, like the one you can get with a base converter, because the ESN number has a different algorithm.
What is an ESN?
Every cellular company has a computer that has all of the series of numbers that are assigned to a cellular company by a government agency. But when you want a specific number to work you have to register it with a Electronic Serial Number (ESN). Every serial number is unique.
For example, if your number is 662-01-61 that number will have an Electronic Serial Number assigned to it. And it won't matter if someone else program another phone with the same number (clone), because your number will only work on your phone because it's your phones serial number that is registered.
Thanks to Saulo David Briseņo Gonzalez of Telcel, Mexico, for this explanation.