It is a nialpdrome in base 16.
It is a congruent number.
It is an unprimeable number.
3990 is a gapful number since it is divisible by the number (30) formed by its first and last digit.
It is a practical number, because each smaller number is the sum of distinct divisors of 3990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (5760).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
3990 is a wasteful number, since it uses less digits than its factorization.
3990 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 36.
The square root of 3990 is about 63.1664467894. The cubic root of 3990 is about 15.8607711386.
Subtracting from 3990 its sum of digits (21), we obtain a square (3969 = 632).
3990 divided by its sum of digits (21) gives a triangular number (190 = T19).
The spelling of 3990 in words is "three thousand, nine hundred ninety".