391997648 has 60 divisors (see below), whose sum is σ = 921949920. Its totient is φ = 160687296.

The previous prime is 391997633. The next prime is 391997677. The reversal of 391997648 is 846799193.

It is a Harshad number since it is a multiple of its sum of digits (56).

It is a junction number, because it is equal to n+sod(n) for n = 391997593 and 391997602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7163 + ... + 28901.

It is an arithmetic number, because the mean of its divisors is an integer number (15365832).

Almost surely, 2^391997648 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 391997648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (460974960).

391997648 is an abundant number, since it is smaller than the sum of its proper divisors (529952272).

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

391997648 is a wasteful number, since it uses less digits than its factorization.

391997648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21784 (or 21771 counting only the distinct ones).

The product of its digits is 2939328, while the sum is 56.

The square root of 391997648 is about 19798.9304761646. The cubic root of 391997648 is about 731.8596782794.

The spelling of 391997648 in words is "three hundred ninety-one million, nine hundred ninety-seven thousand, six hundred forty-eight".