What name is given to the musical symbol that resembles a hashtag?

In music, sharp, dièse (from French), or diesis (from Greek) means higher in pitch. More specifically, in musical notation, sharp means "higher in pitch by one semitone (half step)". Sharp is the opposite of flat, which is a lowering of pitch.

An associated sharp symbol that resembles the number sign "#", ♯, occurs in key signatures or as an accidental. For instance, the music below has a key signature with three sharps (indicating either A major or F♯ minor, the relative minor) and the note, A♯, has a sharp accidental.

The sharp symbol (♯) resembles the number (hash) sign (#). Both signs have two sets of parallel double-lines. However, a correctly drawn sharp sign has two slanted parallel lines that rise from left to right, to avoid obscuring the staff lines. The number sign, in contrast, has two completely horizontal strokes in this place. In addition, while the sharp also always has two perfectly vertical lines, the number sign (#) may or may not contain perfectly vertical lines (according to typeface and writing style).