391889988 has 168 divisors, whose sum is σ = 1195759488. Its totient is φ = 110014848.

The previous prime is 391889983. The next prime is 391890011. The reversal of 391889988 is 889988193.

391889988 is a `hidden beast` number, since 391 + 88 + 99 + 88 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is not an unprimeable number, because it can be changed into a prime (391889983) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 1489945 + ... + 1490207.

It is an arithmetic number, because the mean of its divisors is an integer number (7117616).

Almost surely, 2^391889988 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 391889988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (597879744).

391889988 is an abundant number, since it is smaller than the sum of its proper divisors (803869500).

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

391889988 is a wasteful number, since it uses less digits than its factorization.

391889988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 365 (or 348 counting only the distinct ones).

The product of its digits is 8957952, while the sum is 63.

The square root of 391889988 is about 19796.2114557306. The cubic root of 391889988 is about 731.7926717317.

The spelling of 391889988 in words is "three hundred ninety-one million, eight hundred eighty-nine thousand, nine hundred eighty-eight".