join is failing on large numbers somehow

I have 2 files to join
file 1
99910287    1
99978720    1
99980081    1
99980180    2
99980281    1
99980406    1
99980932    1
99982402    1
100002132   1
100002162   2
100002166   3
file 2 contains
99980081    1
100002129   1
100002136   2
100002162   3

Join fails to join properly only giving 99980081
if I prefix the 9's with a 0 join does not fail

Barry