find two numbers between 60 and 70 which exactly divides 2^48 - 1
well, 2^48-1 = (2^24-1)(2^24+1)
Both of those are way too big, so
2^24-1 = (2^12-1)(2^12+1)
still too big, so
2^12-1 = (2^6-1)(2^6+1) = 63*65
So,
2^48-1 = 63*65(2^12+1)(2^24+1)