391638 has 16 divisors (see below), whose sum is σ = 843696. Its totient is φ = 120480.

The previous prime is 391631. The next prime is 391639. The reversal of 391638 is 836193.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2433 + ... + 2588.

It is an arithmetic number, because the mean of its divisors is an integer number (52731).

2³⁹¹⁶³⁸ is an apocalyptic number.

391638 is an abundant number, since it is smaller than the sum of its proper divisors (452058).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

391638 is a wasteful number, since it uses less digits than its factorization.

391638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5039.

The product of its digits is 3888, while the sum is 30.

The square root of 391638 is about 625.8098752816. The cubic root of 391638 is about 73.1635788835.

The spelling of 391638 in words is "three hundred ninety-one thousand, six hundred thirty-eight".