391643 has 4 divisors (see below), whose sum is σ = 447600. Its totient is φ = 335688.

The previous prime is 391639. The next prime is 391661. The reversal of 391643 is 346193.

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

It is a cyclic number.

It is not a de Polignac number, because 391643 - 2² = 391639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391613) 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, 27968 + ... + 27981.

It is an arithmetic number, because the mean of its divisors is an integer number (111900).

2³⁹¹⁶⁴³ is an apocalyptic number.

391643 is a deficient number, since it is larger than the sum of its proper divisors (55957).

391643 is an equidigital number, since it uses as much as digits as its factorization.

391643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55956.

The product of its digits is 1944, while the sum is 26.

The square root of 391643 is about 625.8138700924. The cubic root of 391643 is about 73.1638902393.

The spelling of 391643 in words is "three hundred ninety-one thousand, six hundred forty-three".