921091691 has 16 divisors (see below), whose sum is σ = 1039795680. Its totient is φ = 810190080.

The previous prime is 921091687. The next prime is 921091697. The reversal of 921091691 is 196190129.

It is a cyclic number.

It is not a de Polignac number, because 921091691 - 2² = 921091687 is a prime.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (921091697) 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, 2825 + ... + 43013.

It is an arithmetic number, because the mean of its divisors is an integer number (64987230).

Almost surely, 2^921091691 is an apocalyptic number.

921091691 is a deficient number, since it is larger than the sum of its proper divisors (118703989).

921091691 is a wasteful number, since it uses less digits than its factorization.

921091691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40286.

The product of its (nonzero) digits is 8748, while the sum is 38.

The square root of 921091691 is about 30349.4924339766. The cubic root of 921091691 is about 972.9733721513.

The spelling of 921091691 in words is "nine hundred twenty-one million, ninety-one thousand, six hundred ninety-one".