In Hebrew, numbers have meaning. The age of the patriarchs is significant, in that the ages are all made up of multiples that add up to 17, which is the the combination of 10 (the number of ordinal perfection) and 7 (the number of spiritual perfection), thus the meaning for 17 is the perfection of spiritual order.
Abraham lived 175 years = 5 x 5 x 7
Issac lived 180 years = 6 x 6 x 5
Jacob lived 147 years = 7 x 7 x 3
17 is also the 7th prime number (1,3,5,7,11,13,17)