In numerology it is the number 3. Look up the symbolism of the number 3 in whatever culture you found this number in. Most large numbers are broken down into single digits by adding them 1+1+1=3 or if they come out to be larger 6+6+6=18 the sum is seperated and added again 1+8=9 which is identical to 3+3+3=9
Numerology is pretty simple in its most basic form.
Some cultures and mythologies, such as the Torah, have certain repeating numbers which are just considered sacred. Most are the sum of 1, 3 or 9. If it relates to the age of someone, the older someone was when they died demonstrated their status among their god(s) or the extent of the individual's wisdom.