397991664 has 80 divisors (see below), whose sum is σ = 1305591040. Its totient is φ = 113711040.

The previous prime is 397991623. The next prime is 397991677. The reversal of 397991664 is 466199793.

397991664 is a `hidden beast` number, since 397 + 99 + 166 + 4 = 666.

It is a super-2 number, since 2×397991664² = 316794729226977792, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 397991664.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 62782 + ... + 68829.

It is an arithmetic number, because the mean of its divisors is an integer number (16319888).

Almost surely, 2^397991664 is an apocalyptic number.

It is an amenable number.

397991664 is an abundant number, since it is smaller than the sum of its proper divisors (907599376).

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

397991664 is a wasteful number, since it uses less digits than its factorization.

397991664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131635 (or 131623 counting only the distinct ones).

The product of its digits is 2204496, while the sum is 54.

The square root of 397991664 is about 19949.7284192041. The cubic root of 397991664 is about 735.5711013239.

The spelling of 397991664 in words is "three hundred ninety-seven million, nine hundred ninety-one thousand, six hundred sixty-four".