397840 has 20 divisors (see below), whose sum is σ = 925164. Its totient is φ = 159104.

The previous prime is 397829. The next prime is 397849. The reversal of 397840 is 48793.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 200704 + 197136 = 448^2 + 444^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (397849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2407 + ... + 2566.

397840 is a Friedman number, since it can be written as 49730*8, using all its digits and the basic arithmetic operations.

2³⁹⁷⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

397840 is an abundant number, since it is smaller than the sum of its proper divisors (527324).

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

397840 is a wasteful number, since it uses less digits than its factorization.

397840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4986 (or 4980 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 31.

The square root of 397840 is about 630.7455905514. The cubic root of 397840 is about 73.5477653949.

The spelling of 397840 in words is "three hundred ninety-seven thousand, eight hundred forty".