397921 has 2 divisors, whose sum is σ = 397922. Its totient is φ = 397920.

The previous prime is 397907. The next prime is 397939. The reversal of 397921 is 129793.

397921 is nontrivially palindromic in base 8.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 342225 + 55696 = 585^2 + 236^2 .

It is an emirp because it is prime and its reverse (129793) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 397921 - 2¹¹ = 395873 is a prime.

It is a super-2 number, since 2×397921² = 316682244482, which contains 22 as substring.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (397951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 198960 + 198961.

It is an arithmetic number, because the mean of its divisors is an integer number (198961).

2³⁹⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

397921 is a deficient number, since it is larger than the sum of its proper divisors (1).

397921 is an equidigital number, since it uses as much as digits as its factorization.

397921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3402, while the sum is 31.

The square root of 397921 is about 630.8097970070. The cubic root of 397921 is about 73.5527564840.

It can be divided in two parts, 39792 and 1, that added together give a palindrome (39793).

The spelling of 397921 in words is "three hundred ninety-seven thousand, nine hundred twenty-one".