391781997440 has 64 divisors (see below), whose sum is σ = 938021800320. Its totient is φ = 156475545600.

The previous prime is 391781997403. The next prime is 391781997461. The reversal of 391781997440 is 44799187193.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40016 + ... + 886095.

It is an arithmetic number, because the mean of its divisors is an integer number (14656590630).

Almost surely, 2^391781997440 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 391781997440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (469010900160).

391781997440 is an abundant number, since it is smaller than the sum of its proper divisors (546239802880).

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

391781997440 is an equidigital number, since it uses as much as digits as its factorization.

391781997440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 926791 (or 926779 counting only the distinct ones).

The product of its (nonzero) digits is 13716864, while the sum is 62.

The spelling of 391781997440 in words is "three hundred ninety-one billion, seven hundred eighty-one million, nine hundred ninety-seven thousand, four hundred forty".