The 12 notes in an octave are commonly named C, C#, D, D#, E, F, F#, G, G#, A, A#, B.
The concert pitch tuning of the middle A in the musical scale is 440 Hz. This is common tuning in the US and Britain, but this reference pitch varies in different countries and has varied throughout the centuries. The middle A is often called A4 in musical software.
Each octave is a doubling of the frequency, so A5 would be A5 = 2 * A4 = 2 * 440 Hz = 880 Hz. Since there are 12 note intervals in an octave each single note increment is a factor of 2(1/12) = 20.08333... = 1.0594630943592953