391645 has 16 divisors (see below), whose sum is σ = 506160. Its totient is φ = 290304.

The previous prime is 391639. The next prime is 391661. The reversal of 391645 is 546193.

391645 = T₈₆ + T₈₇ + ... + T₁₄₃.

It can be written as a sum of positive squares in 8 ways, for example, as 15876 + 375769 = 126^2 + 613^2 .

It is a cyclic number.

It is not a de Polignac number, because 391645 - 2⁵ = 391613 is a prime.

391645 is a lucky number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5329 + ... + 5401.

It is an arithmetic number, because the mean of its divisors is an integer number (31635).

2³⁹¹⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

391645 is a deficient number, since it is larger than the sum of its proper divisors (114515).

391645 is a wasteful number, since it uses less digits than its factorization.

391645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144.

The product of its digits is 3240, while the sum is 28.

The square root of 391645 is about 625.8154680095. The cubic root of 391645 is about 73.1640147809.

The spelling of 391645 in words is "three hundred ninety-one thousand, six hundred forty-five".