A number theory problem by A Former Brilliant Member
Number Theory
Level
3
Find the missing number 4, 6, 12, 18, 30, 42, 60, 72, 102, 108, ?
The answer is 138.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
The series lists numbers that are flanked by two prime numbers. 4 (3 and 5 are prime). 6 (5 and 7 are prime). 12 (11 and 13 are prime). 18 (17 and 19 are prime). 30 (29 and 31 are prime). 42 (41 and 43 are prime). 60 (59 and 61 are prime). 72 (71 and 73 are prime). 102 (101 and 103 are prime). 108 (107 and 109 are prime). Therefore the next number is 138 (137 and 139 are prime).