What is the palindrome number? Write one 9 digits palindrome number.

123454321

Step-by-step explanation:

A palindrome word or number is a word or number that reads the same forwards and backwards, for example

"civic" and "level" are examples of 5-letter palindrome words.

1221 and 2332 are 4-digit palindrome numbers.

It is easy to construct a palindrome number; start from 1 and go increasing digits until reaching half the number, then go countdown.

For example

123454321 is an example of a 9-digit palindrome number.

There are infinite many of them.