391957 has 4 divisors (see below), whose sum is σ = 394956. Its totient is φ = 388960.

The previous prime is 391939. The next prime is 391961. The reversal of 391957 is 759193.

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

It can be written as a sum of positive squares in 2 ways, for example, as 224676 + 167281 = 474^2 + 409^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-391957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391907) 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, 1294 + ... + 1567.

It is an arithmetic number, because the mean of its divisors is an integer number (98739).

2³⁹¹⁹⁵⁷ is an apocalyptic number.

It is an amenable number.

391957 is a deficient number, since it is larger than the sum of its proper divisors (2999).

391957 is a wasteful number, since it uses less digits than its factorization.

391957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2998.

The product of its digits is 8505, while the sum is 34.

The square root of 391957 is about 626.0646931428. The cubic root of 391957 is about 73.1834380797.

Subtracting 391957 from its reverse (759193), we obtain a square (367236 = 606²).

The spelling of 391957 in words is "three hundred ninety-one thousand, nine hundred fifty-seven".