397991 has 8 divisors (see below), whose sum is σ = 439824. Its totient is φ = 357120.

The previous prime is 397981. The next prime is 398011. The reversal of 397991 is 199793.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 397991 - 2¹⁴ = 381607 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (397921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 881 + ... + 1253.

It is an arithmetic number, because the mean of its divisors is an integer number (54978).

2³⁹⁷⁹⁹¹ is an apocalyptic number.

397991 is a deficient number, since it is larger than the sum of its proper divisors (41833).

397991 is a wasteful number, since it uses less digits than its factorization.

397991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 481.

The product of its digits is 15309, while the sum is 38.

The square root of 397991 is about 630.8652788036. The cubic root of 397991 is about 73.5570692254.

The spelling of 397991 in words is "three hundred ninety-seven thousand, nine hundred ninety-one".