Most mathematical symbols live in the Mathematical Operators block. A few everyday ones are older and live in Latin-1: × U+00D7, ÷ U+00F7 and ± U+00B1.
Several math symbols have lookalikes with different meanings. The minus sign − U+2212 is not the hyphen-minus - U+002D; ∑ U+2211 N-ARY SUMMATION is not the Greek letter Σ U+03A3; ∆ U+2206 INCREMENT is not Δ U+0394; and the micro sign µ U+00B5 turns into Greek μ U+03BC under NFKC normalization. The ohm sign Ω U+2126 is even stricter: every normalization form replaces it with Greek Ω U+03A9. Use the math character when you mean the math symbol, and normalize text before comparing it.
Click any symbol to copy it. Names link to the full character page with every encoding.