Is an NI number still issued if you leave the UK while under 16?

Hello, Could you tell me. If you're born in the UK and have a UK birth certificate, then move to an EU country at a young age but then return some 40 years later holding dual nationality, is an NI number still issued at birth or 16 years old? If so and you don't know the number, how do you find out what it is? Thanks in advance.

Hi,
If you have returned to the UK, please contact the National Insurance helpline or you can complete a form CA5403 - Get your National Insurance number by post 
Alternatively, you can see if you already have a National Insurance number by verifying your identity through a personal tax account:
Personal tax account: sign in or set up 
NI Helpline:
Number - 0300 200 3500
Overseas - +44 191 203 7010
Open - Monday to Friday: 8am to 6pm, Closed on Saturdays, Sundays and Bank Holidays.
If you have not been assigned a National Insurance number, you will need to apply with the Department for Work and Pensions:
Apply for a National Insurance number: How to apply 
Thank you.