391644 has 72 divisors (see below), whose sum is σ = 1153152. Its totient is φ = 110880.

The previous prime is 391639. The next prime is 391661. The reversal of 391644 is 446193.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

391644 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 23 ways as a sum of consecutive naturals, for example, 9087 + ... + 9129.

It is an arithmetic number, because the mean of its divisors is an integer number (16016).

2³⁹¹⁶⁴⁴ 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 391644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (576576).

391644 is an abundant number, since it is smaller than the sum of its proper divisors (761508).

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

391644 is a wasteful number, since it uses less digits than its factorization.

391644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87 (or 82 counting only the distinct ones).

The product of its digits is 2592, while the sum is 27.

The square root of 391644 is about 625.8146690515. The cubic root of 391644 is about 73.1639525101.

It can be divided in two parts, 391 and 644, that added together give a triangular number (1035 = T₄₅).

The spelling of 391644 in words is "three hundred ninety-one thousand, six hundred forty-four".