397721 has 2 divisors, whose sum is σ = 397722. Its totient is φ = 397720.

The previous prime is 397697. The next prime is 397723. The reversal of 397721 is 127793.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 265225 + 132496 = 515^2 + 364^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-397721 is a prime.

Together with 397723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (397723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 198860 + 198861.

It is an arithmetic number, because the mean of its divisors is an integer number (198861).

2³⁹⁷⁷²¹ is an apocalyptic number.

It is an amenable number.

397721 is a deficient number, since it is larger than the sum of its proper divisors (1).

397721 is an equidigital number, since it uses as much as digits as its factorization.

397721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2646, while the sum is 29.

The square root of 397721 is about 630.6512506925. The cubic root of 397721 is about 73.5404315782.

The spelling of 397721 in words is "three hundred ninety-seven thousand, seven hundred twenty-one".