Which of the following numbers has the largest number of unique prime factors?: {85, 138, 317, 207}

1 Answer
Apr 29, 2016

#138# has the largest number of unique prime factors.

Explanation:

Prime factors of #85# are #5# and #17# as #85=5xx17#

Prime factors of #138# are #2#, #3# and #23# as #138=2xx3xx23#

#317# is itself prime as it does not have any factor other than #1# and itself.

Prime factors of #207# are #3# and #23# as #207=3xx3xx23#

Hence, #138# has the largest number of unique prime factors.