391021920 has 288 divisors, whose sum is σ = 1411693920. Its totient is φ = 98426880.

The previous prime is 391021907. The next prime is 391021927. The reversal of 391021920 is 29120193.

It is a tau number, because it is divible by the number of its divisors (288).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391021927) 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 47 ways as a sum of consecutive naturals, for example, 2184391 + ... + 2184569.

It is an arithmetic number, because the mean of its divisors is an integer number (4901715).

Almost surely, 2^391021920 is an apocalyptic number.

391021920 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 391021920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (705846960).

391021920 is an abundant number, since it is smaller than the sum of its proper divisors (1020672000).

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

391021920 is a wasteful number, since it uses less digits than its factorization.

391021920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278 (or 267 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 391021920 is about 19774.2741965413. The cubic root of 391021920 is about 731.2519456446.

The spelling of 391021920 in words is "three hundred ninety-one million, twenty-one thousand, nine hundred twenty".