3990 has 32 divisors (see below), whose sum is σ = 11520. Its totient is φ = 864.

The previous prime is 3989. The next prime is 4001. The reversal of 3990 is 993.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a nialpdrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 201 + ... + 219.

It is an arithmetic number, because the mean of its divisors is an integer number (360).

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).

3990 is an abundant number, since it is smaller than the sum of its proper divisors (7530).

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 product of its (nonzero) digits is 243, while the sum is 21.

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".