391990505 has 16 divisors (see below), whose sum is σ = 514128384. Its totient is φ = 285623040.

The previous prime is 391990457. The next prime is 391990507. The reversal of 391990505 is 505099193.

It is not a de Polignac number, because 391990505 - 2²⁸ = 123555049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391990507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71747 + ... + 77016.

It is an arithmetic number, because the mean of its divisors is an integer number (32133024).

Almost surely, 2^391990505 is an apocalyptic number.

It is an amenable number.

391990505 is a deficient number, since it is larger than the sum of its proper divisors (122137879).

391990505 is a wasteful number, since it uses less digits than its factorization.

391990505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148816.

The product of its (nonzero) digits is 54675, while the sum is 41.

The square root of 391990505 is about 19798.7500868110. The cubic root of 391990505 is about 731.8552329250.

The spelling of 391990505 in words is "three hundred ninety-one million, nine hundred ninety thousand, five hundred five".