396821 has 4 divisors (see below), whose sum is σ = 405312. Its totient is φ = 388332.

The previous prime is 396733. The next prime is 396833. The reversal of 396821 is 128693.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 396821 - 2¹⁸ = 134677 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (396871) 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, 4175 + ... + 4268.

It is an arithmetic number, because the mean of its divisors is an integer number (101328).

2³⁹⁶⁸²¹ is an apocalyptic number.

It is an amenable number.

396821 is a deficient number, since it is larger than the sum of its proper divisors (8491).

396821 is an equidigital number, since it uses as much as digits as its factorization.

396821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8490.

The product of its digits is 2592, while the sum is 29.

The square root of 396821 is about 629.9372984671. The cubic root of 396821 is about 73.4849183118.

The spelling of 396821 in words is "three hundred ninety-six thousand, eight hundred twenty-one".