987191891 has 8 divisors (see below), whose sum is σ = 1155737184. Its totient is φ = 825526080.

The previous prime is 987191879. The next prime is 987191903. The reversal of 987191891 is 198191789.

It is an interprime number because it is at equal distance from previous prime (987191879) and next prime (987191903).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-987191891 is a prime.

It is not an unprimeable number, because it can be changed into a prime (987191801) 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, 1719560 + ... + 1720133.

It is an arithmetic number, because the mean of its divisors is an integer number (144467148).

Almost surely, 2^987191891 is an apocalyptic number.

987191891 is a deficient number, since it is larger than the sum of its proper divisors (168545293).

987191891 is a wasteful number, since it uses less digits than its factorization.

987191891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3439741.

The product of its digits is 326592, while the sum is 53.

The square root of 987191891 is about 31419.6099753005. The cubic root of 987191891 is about 995.7122719980.

The spelling of 987191891 in words is "nine hundred eighty-seven million, one hundred ninety-one thousand, eight hundred ninety-one".