391635987 has 16 divisors (see below), whose sum is σ = 553301280. Its totient is φ = 245553152.

The previous prime is 391635949. The next prime is 391635991. The reversal of 391635987 is 789536193.

It is a cyclic number.

It is not a de Polignac number, because 391635987 - 2⁷ = 391635859 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is not an unprimeable number, because it can be changed into a prime (391635947) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 120439 + ... + 123647.

It is an arithmetic number, because the mean of its divisors is an integer number (34581330).

Almost surely, 2^391635987 is an apocalyptic number.

391635987 is a deficient number, since it is larger than the sum of its proper divisors (161665293).

391635987 is a wasteful number, since it uses less digits than its factorization.

391635987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5622.

The product of its digits is 1224720, while the sum is 51.

The square root of 391635987 is about 19789.7950216772. The cubic root of 391635987 is about 731.6345353084.

It can be divided in two parts, 39163 and 5987, that added together give a triangular number (45150 = T₃₀₀).

The spelling of 391635987 in words is "three hundred ninety-one million, six hundred thirty-five thousand, nine hundred eighty-seven".