How do I type the ⅀ double-struck n-ary summation symbol?

On Windows, type 2140 and press Alt+X. On Linux press Ctrl+Shift+U then 2140. On any system the quickest route is the copy button on this page.

What is the code for ⅀?

Double-Struck N-Ary Summation is U+2140 and in LaTeX as \Bbbsum. In UTF-8 it takes 3 bytes. The table above lists every escape format.

Will ⅀ survive being pasted anywhere?

Not always. Double-Struck N-Ary Summation is a compatibility character: any system that applies Unicode NFKC normalisation — search indexes, usernames, identifiers — replaces it with ∑. Use it for display, not where text is normalised.

U+2140 · Math symbol

LaTeX

\Bbbsum

Double-Struck N-Ary Summation Symbol ⅀

⅀ is double-struck n-ary summation, U+2140 — \Bbbsum in LaTeX. It was added in Unicode 3.2, and Unicode files it under Math symbol.

Codes & technical data

Unicode	`U+2140`
HTML hex	`⅀`
HTML decimal	`⅀`
CSS	`\2140`
JavaScript	`\u{2140}`
Python	`\U00002140`
Java / C#	`\u2140`
Rust	`\u{2140}`
Swift	`\u{2140}`
PHP	`\u{2140}`
URL encoded	`%E2%85%80`
UTF-8 bytes	`E2 85 80`
UTF-16 bytes	`2140`
Base64	`4oWA`
Decimal	`8512`
LaTeX	`\Bbbsum`
Decomposes to	∑ (font form)
Category	Math symbol (Sm)
Introduced	Unicode 3.2

Will ⅀ survive being pasted?

Normalisation. No. Anything that applies NFKC — search indexes, usernames, domain names, programming identifiers — rewrites ⅀ as ∑. Safe for display, not for storage.
Legacy encodings. ⅀ is Unicode-only — it has no Latin-1 equivalent, so a system stuck on an 8-bit encoding cannot represent it.
Size. 3 bytes in UTF-8. Character-limited fields — SMS, bios, some form validators — usually count bytes, not characters.

Nearby in Letterlike Symbols

Characters built out of letters but treated as symbols — ℃ ℉ №, the trademark and service marks, and the script and blackletter letters that mathematics uses as distinct variables. Most normalise back to plain letters, which is worth knowing before pasting one into a password field.

All 34 characters in Letterlike Symbols →

How to type ⅀

Windows	Type `2140` then press `Alt`+`X`
macOS	Press `Ctrl`+`Cmd`+`Space`, then search for “double-struck n-ary summation”
Linux	Press `Ctrl`+`Shift`+`U`, type `2140`, press `Enter`
HTML	`⅀`

About Unicode’s Math symbol category

Unicode classifies this as a mathematical symbol, which means software that lays out formulas treats it as an operator or relation and gives it spacing accordingly, rather than setting it tight against its neighbours like a letter.

Frequently asked questions

How do I type the ⅀ double-struck n-ary summation symbol?: On Windows, type 2140 and press Alt+X. On Linux press Ctrl+Shift+U then 2140. On any system the quickest route is the copy button on this page.
What is the code for ⅀?: Double-Struck N-Ary Summation is U+2140 and in LaTeX as \Bbbsum. In UTF-8 it takes 3 bytes. The table above lists every escape format.
Will ⅀ survive being pasted anywhere?: Not always. Double-Struck N-Ary Summation is a compatibility character: any system that applies Unicode NFKC normalisation — search indexes, usernames, identifiers — replaces it with ∑. Use it for display, not where text is normalised.