391561 has 8 divisors (see below), whose sum is σ = 428544. Its totient is φ = 356160.

The previous prime is 391553. The next prime is 391579. The reversal of 391561 is 165193.

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 391561 - 2³ = 391553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (391661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 156 + ... + 898.

It is an arithmetic number, because the mean of its divisors is an integer number (53568).

2³⁹¹⁵⁶¹ is an apocalyptic number.

391561 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

It is an amenable number.

391561 is a deficient number, since it is larger than the sum of its proper divisors (36983).

391561 is a wasteful number, since it uses less digits than its factorization.

391561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 791.

The product of its digits is 810, while the sum is 25.

The square root of 391561 is about 625.7483519755. The cubic root of 391561 is about 73.1587836688.

It can be divided in two parts, 39 and 1561, that added together give a square (1600 = 40²).

The spelling of 391561 in words is "three hundred ninety-one thousand, five hundred sixty-one".