8991681 has 4 divisors (see below), whose sum is σ = 11988912. Its totient is φ = 5994452.

The previous prime is 8991679. The next prime is 8991713. The reversal of 8991681 is 1861998.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 8991681 - 2¹ = 8991679 is a prime.

It is a super-2 number, since 2×8991681² = 161700654411522, which contains 22 as substring.

It is an Ulam number.

It is a Curzon number.

8991681 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (8991611) 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, 1498611 + ... + 1498616.

It is an arithmetic number, because the mean of its divisors is an integer number (2997228).

Almost surely, 2^8991681 is an apocalyptic number.

It is an amenable number.

8991681 is a deficient number, since it is larger than the sum of its proper divisors (2997231).

8991681 is a wasteful number, since it uses less digits than its factorization.

8991681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2997230.

The product of its digits is 31104, while the sum is 42.

The square root of 8991681 is about 2998.6131794548. The cubic root of 8991681 is about 207.9442728545.

The spelling of 8991681 in words is "eight million, nine hundred ninety-one thousand, six hundred eighty-one".