391664 has 40 divisors (see below), whose sum is σ = 937440. Its totient is φ = 154368.

The previous prime is 391661. The next prime is 391679. The reversal of 391664 is 466193.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1322 + ... + 1590.

It is an arithmetic number, because the mean of its divisors is an integer number (23436).

2³⁹¹⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 391664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (468720).

391664 is an abundant number, since it is smaller than the sum of its proper divisors (545776).

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

391664 is a wasteful number, since it uses less digits than its factorization.

391664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297 (or 291 counting only the distinct ones).

The product of its digits is 3888, while the sum is 29.

The square root of 391664 is about 625.8306480191. The cubic root of 391664 is about 73.1651979049.

Subtracting 391664 from its reverse (466193), we obtain a square (74529 = 273²).

The spelling of 391664 in words is "three hundred ninety-one thousand, six hundred sixty-four".