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Very Odd Numbers

 Published on Saturday, 13th December 2025, 04:00 pm and solved by 635
Difficulty: Level 8 [23%]

Problem 974

A very odd number is a number which contains only odd digits and is divisible by $105$. Further each odd digit occurs an odd number of times.

Define $\Theta (n)$ be the $n$th very odd number, then $\Theta (1) = 1117935$ and $\Theta(10^3) = 11137955115$.

Find $\Theta(10^{16})$.



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