8991665987 has 4 divisors (see below), whose sum is σ = 8991865800. Its totient is φ = 8991466176.

The previous prime is 8991665981. The next prime is 8991665989. The reversal of 8991665987 is 7895661998.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 8991665987 - 2²⁸ = 8723230531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8991665981) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2768 + ... + 134130.

It is an arithmetic number, because the mean of its divisors is an integer number (2247966450).

Almost surely, 2^8991665987 is an apocalyptic number.

8991665987 is a deficient number, since it is larger than the sum of its proper divisors (199813).

8991665987 is a wasteful number, since it uses less digits than its factorization.

8991665987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199812.

The product of its digits is 58786560, while the sum is 68.

The square root of 8991665987 is about 94824.3955266787. The cubic root of 8991665987 is about 2079.4415712275.

The spelling of 8991665987 in words is "eight billion, nine hundred ninety-one million, six hundred sixty-five thousand, nine hundred eighty-seven".