391561801920 has 336 divisors, whose sum is σ = 1403836001568. Its totient is φ = 103882383360.

The previous prime is 391561801859. The next prime is 391561801921. The reversal of 391561801920 is 29108165193.

391561801920 is a `hidden beast` number, since 3 + 9 + 1 + 5 + 618 + 0 + 1 + 9 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (391561801921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 15305940 + ... + 15331500.

It is an arithmetic number, because the mean of its divisors is an integer number (4178083338).

Almost surely, 2^391561801920 is an apocalyptic number.

391561801920 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 391561801920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (701918000784).

391561801920 is an abundant number, since it is smaller than the sum of its proper divisors (1012274199648).

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

391561801920 is a wasteful number, since it uses less digits than its factorization.

391561801920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25790 (or 25768 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 45.

The spelling of 391561801920 in words is "three hundred ninety-one billion, five hundred sixty-one million, eight hundred one thousand, nine hundred twenty".