3 x 7 = 21 You can put "to the first power" after the three and the seven, but it's not necessary.
The prime factorization of 50 using exponents is 21 x 52
3 x 7 = 21 No exponents necessary.
3 x 7 = 21
10 = 21*51
21 x 33
54 = 21 x 33
1250 = 21 x 54
18 = 21 x 32
It is: 21*71*111 = 154
21 x 831 = 166
14 = 21 x 71
94 = 21 x 471