data/problems/145.yml
---
:id: 145
:name: How many reversible numbers are there below one-billion?
:url: https://projecteuler.net/problem=145
:content: |+
Some positive integers _n_ have the property that the sum [_n_ + reverse(_n_)] consists entirely of odd (decimal) digits. For instance, 36 + 63 = 99 and 409 + 904 = 1313. We will call such numbers _reversible_; so 36, 63, 409, and 904 are reversible. Leading zeroes are not allowed in either _n_ or reverse(_n_).
There are 120 reversible numbers below one-thousand.
How many reversible numbers are there below one-billion (10<sup>9</sup>)?