391971 has 4 divisors (see below), whose sum is σ = 522632. Its totient is φ = 261312.

The previous prime is 391967. The next prime is 391987. The reversal of 391971 is 179193.

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

It is not a de Polignac number, because 391971 - 2² = 391967 is a prime.

It is a D-number.

It is a Duffinian number.

391971 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (391921) 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, 65326 + ... + 65331.

It is an arithmetic number, because the mean of its divisors is an integer number (130658).

2³⁹¹⁹⁷¹ is an apocalyptic number.

391971 is a deficient number, since it is larger than the sum of its proper divisors (130661).

391971 is a wasteful number, since it uses less digits than its factorization.

391971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130660.

The product of its digits is 1701, while the sum is 30.

The square root of 391971 is about 626.0758739961. The cubic root of 391971 is about 73.1843093963.

The spelling of 391971 in words is "three hundred ninety-one thousand, nine hundred seventy-one".