What do you call a number which is the same written backwards? Example 16061.
Palindrome /…/ noun a word, phrase, or sequence that reads the same backward as forward
In the definition, a sequence refers to number chains. If you didn't want to be completely on the nose about it, you could work in the phrase mirror image to describe what you need as well.
The correct mathematical term is a palindromic number (or a numerical palindrome).
To quote Wikipedia:
A palindromic number or numeral palindrome is a number that remains the same when its digits are reversed. Like 16461, for example, it is "symmetrical". The term palindromic is derived from palindrome, which refers to a word (such as rotor or racecar) whose spelling is unchanged when its letters are reversed.
And for a more mathematical definition from Wolfram:
A palindromic number is a number (in some base b) that is the same when written forwards or backwards, i.e., of the form a_1a_2...a_2a_1. The first few palindromic numbers are therefore are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, ... (OEIS A002113).
These in turn are used to form the derived terms palindromic prime and strictly non-palindromic number.