Why are there missing EIP numbers?

[xhliu]

I am looking at all EIPs https://eips.ethereum.org/all and notice the numbers are not consecutive. For example, there is no EIP 9 to 19. Are they withdrawn?

[abcoathup]

EIP numbers are generally the PR number in this repo (unless an editor assigns a different number). See EIP-1.
If you check some of the PRs I assume they were making changes and not creating a new EIP

[Pandapip1]

There are a few other reasons:

• Github issues also increase the PR number (for example, https://github.com/ethereum/EIPs/pull/5077 redirects to this issue despite not being a PR)
• Some PRs aren't merged yet or have been closed. For example, I once opened a PR for an EIP before realizing that it was actually unimplementable (oops), and so I closed it.
• Sometimes, to prevent number sniping (e.g. MULDIV instruction #5000), a different EIP number is assigned.
• Spambots sometimes create Github issues. For example Create Sjenica1 #4843