What is the greatest prime factor of 78?

1 Answer
Dec 25, 2016

#13# is the greatest prime factor of #78#.

Explanation:

Last digit of #78# is #8#, an even number and hence divisible by #2#. Further, sum of the digits is #7+8=15#, divisible by #3#.

Hence #78# is divisible by prime numbers #2# ad #3#. Dividing #78# by these numbers, we get #13# and hence

#78=2xx3xx13#

Hence, #13# is the greatest prime factor of #78#.