3990639 has 4 divisors (see below), whose sum is σ = 5320856. Its totient is φ = 2660424.

The previous prime is 3990619. The next prime is 3990641. The reversal of 3990639 is 9360993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9360993 = 3 ⋅3120331.

It is not a de Polignac number, because 3990639 - 2⁵ = 3990607 is a prime.

It is a D-number.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 3990597 and 3990606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3990619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 665104 + ... + 665109.

It is an arithmetic number, because the mean of its divisors is an integer number (1330214).

Almost surely, 2^3990639 is an apocalyptic number.

3990639 is a deficient number, since it is larger than the sum of its proper divisors (1330217).

3990639 is a wasteful number, since it uses less digits than its factorization.

3990639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1330216.

The product of its (nonzero) digits is 39366, while the sum is 39.

The square root of 3990639 is about 1997.6583792030. The cubic root of 3990639 is about 158.6161779625.

The spelling of 3990639 in words is "three million, nine hundred ninety thousand, six hundred thirty-nine".