991815087 has 8 divisors (see below), whose sum is σ = 1323506304. Its totient is φ = 660666968.

The previous prime is 991815053. The next prime is 991815107. The reversal of 991815087 is 780518199.

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 991815087 - 2¹⁰ = 991814063 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991815787) 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, 131493 + ... + 138830.

It is an arithmetic number, because the mean of its divisors is an integer number (165438288).

Almost surely, 2^991815087 is an apocalyptic number.

991815087 is a deficient number, since it is larger than the sum of its proper divisors (331691217).

991815087 is a wasteful number, since it uses less digits than its factorization.

991815087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271549.

The product of its (nonzero) digits is 181440, while the sum is 48.

The square root of 991815087 is about 31493.0958624267. The cubic root of 991815087 is about 997.2642179888.

The spelling of 991815087 in words is "nine hundred ninety-one million, eight hundred fifteen thousand, eighty-seven".