25 is the next number that appears in that sequence.
243
This is a sequence of perfect squares. 12=1, 22=4, 32=9, 42=16, 52=25. The next number is 62=36.
This is a geometric sequence. Each number is multiplied by the same constant, to get the next number. If you divide any number by the previous one, you can find out what this constant is.
the next number in the sequence 1 5 25 125 is 625
27
15
27
The next number is 25 but there are the sequence is infinite so there can be no end to the sequence.
27
This sequence is the squaring of the numbers 1, 3, 5, and 7. The next number is 9^2 = 81.
If you mean: 1 4 9 16 25 then it is 36