M = 0...................on a horizontal line............like the x axis.........31 + 37 = 68............like the 1st stand dev from the mean...................m is undef or infinite for a vertical line...........like the Y axis........

List of First 25 Prime Numbers

Sequence	Prime Number
1	2
2	3
3	5
4	7
5	11
6	13
7	17
8	19
9	23
10	29
11	31
12	37
13	41
14	43
15	47
16	53
17	59
18	61
19	67
20	71
21	73
22	79
23	83
24	89
25	97