Ideally using a superscript 4 to the right of the thing being raised to the power of 4.
Computer languages can use:
1) a double multiplication sign - a double asterisk, eg 2**4 is 2 to the power 4, which is 16; or
2) the caret symbol, eg 2^4 is 2 to the power 4.
The latter (using the caret symbol) is often used when a superscript is impossible, outside computer languages.
4 to the power of 5
4 to the second power
43
45
7x10 to the power of -4
41
10-4
4 then tiny 2
You can write it as 41 or 22 or 160.5 or 82/3 and so on.
6.3*10power of 4
4^(5)
Four to the third power (43) is the same as 4 x 4 x 4 or 64