Using math... NOTE: this may not work on international number if you have over 7 digits... Get your calculator or start calc on your PC: Start/Run/calc and then follow the steps below: 1. Key in the first three digits of your phone number (NOT the area code) 2 Multiply by 80 3. Add 1 4. Multiply by 250 5. Add the last 4 digits of your phone number 6. Add the last 4 digits of your phone number again. 7. Subtract 250 8. Divide number by 2 Do you recognize the answer?