how i can change my mobil number to send the security code ?

Hello there, Graphic Volcano.

The following FAQ provides the answer to the question it seems you are asking:

iCloud: Frequently asked questions about iCloud Keychain

http://support.apple.com/kb/HT5813

How can I set up additional devices to use iCloud Keychain?

Follow the iCloud Keychain setup steps above for each device that you want to add. When you enable iCloud Keychain on an additional device, your other devices that use iCloud Keychain receive a notification requesting approval for the additional device. After you approve the additional device, your iCloud Keychain automatically begins updating on that device.

Thanks for reaching out to Apple Support Communities.

Cheers,

Pedro.

Change it as follows (from http://support.apple.com/kb/TS4644):

• Devices using iOS 7.0.3 or later: Tap Settings > iCloud > Account, then tap Keychain. Check that the phone number listed under Verification Number is correct. If not, enter another phone number.
• Macs using OS X Mavericks v10.9 or later: Choose Apple () menu > System Preferences. Click iCloud, then click Account Details. Check that the phone number listed under Verification number is correct. If not, enter another phone number.