391987105 has 8 divisors (see below), whose sum is σ = 498054312. Its totient is φ = 295143168.

The previous prime is 391987093. The next prime is 391987109. The reversal of 391987105 is 501789193.

It can be written as a sum of positive squares in 4 ways, for example, as 53758224 + 338228881 = 7332^2 + 18391^2 .

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 391987105 - 2⁵ = 391987073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391987109) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2305722 + ... + 2305891.

It is an arithmetic number, because the mean of its divisors is an integer number (62256789).

Almost surely, 2^391987105 is an apocalyptic number.

It is an amenable number.

391987105 is a deficient number, since it is larger than the sum of its proper divisors (106067207).

391987105 is a wasteful number, since it uses less digits than its factorization.

391987105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4611635.

The product of its (nonzero) digits is 68040, while the sum is 43.

The square root of 391987105 is about 19798.6642226187. The cubic root of 391987105 is about 731.8531169596.

The spelling of 391987105 in words is "three hundred ninety-one million, nine hundred eighty-seven thousand, one hundred five".