397439821 has 4 divisors (see below), whose sum is σ = 420818652. Its totient is φ = 374060992.

The previous prime is 397439789. The next prime is 397439851. The reversal of 397439821 is 128934793.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 115670025 + 281769796 = 10755^2 + 16786^2 .

It is a cyclic number.

It is not a de Polignac number, because 397439821 - 2⁵ = 397439789 is a prime.

It is a super-2 number, since 2×397439821² = 315916822633024082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (397439851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11689390 + ... + 11689423.

It is an arithmetic number, because the mean of its divisors is an integer number (105204663).

Almost surely, 2^397439821 is an apocalyptic number.

It is an amenable number.

397439821 is a deficient number, since it is larger than the sum of its proper divisors (23378831).

397439821 is a wasteful number, since it uses less digits than its factorization.

397439821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23378830.

The product of its digits is 326592, while the sum is 46.

The square root of 397439821 is about 19935.8927816138. The cubic root of 397439821 is about 735.2309706490.

The spelling of 397439821 in words is "three hundred ninety-seven million, four hundred thirty-nine thousand, eight hundred twenty-one".