Activate 2FA: Go to Settings > Privacy and Security > Two-Step Verification.
Set a Strong Password: Choose a complex password that is unique to Telegram and not used elsewhere.
Add a Recovery Email: Crucially, link a recovery email address. This email will be used to send a code if you ever forget your 2FA password, preventing you from being locked out. Ensure this email itself is highly secure.
4. Manage and Control Contact Syncing
Disable Syncing (if preferred): Go to Settings > Privacy and Security > Contacts. Consider toggling "Sync Contacts" OFF. This prevents Telegram from uploading your device's entire address book to its servers.
Delete Synced Data: If you've previously synced contacts, tap telegram number database on "Delete Synced Contacts" in the same section. This removes any contact data Telegram stored from your phone's address book. If you leave "Sync Contacts" enabled, it will re-upload them.
5. Review Your Active Sessions Regularly
Go to Settings > Devices (or Active Sessions).
This shows all the devices where your Telegram account is currently logged in.
Terminate Unknown Sessions: If you see any unfamiliar or old devices, immediately select them and choose "Terminate" or "Log out." This revokes their access to your account.
Avoid Manual Sharing: Do not manually type or share your phone number in public Telegram groups, channels, or with people you don't fully trust in private chats.
"Share Contact" Feature: Be mindful when using the "Share Contact" button in a chat; it will send your contact card, which includes your phone number, to the recipient.
Bots and External Services: Only share your phone number with a bot or external service connected to Telegram if you fully trust it and understand why it needs your number (it will always require explicit confirmation).
7. Consider Using an Anonymous Number (Fragment +888)
For the absolute highest level of phone number privacy, you can create a Telegram account using an anonymous +888 number purchased via Telegram's official Fragment platform. These numbers are tied to the TON blockchain and not to your personal identity or a physical SIM card.