891108721 has 4 divisors (see below), whose sum is σ = 938009200. Its totient is φ = 844208244.

The previous prime is 891108709. The next prime is 891108727. The reversal of 891108721 is 127801198.

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 891108721 - 2⁹ = 891108209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (891108727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23450211 + ... + 23450248.

It is an arithmetic number, because the mean of its divisors is an integer number (234502300).

Almost surely, 2^891108721 is an apocalyptic number.

It is an amenable number.

891108721 is a deficient number, since it is larger than the sum of its proper divisors (46900479).

891108721 is a wasteful number, since it uses less digits than its factorization.

891108721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46900478.

The product of its (nonzero) digits is 8064, while the sum is 37.

The square root of 891108721 is about 29851.4442029192. Note that the first 3 decimals coincide. The cubic root of 891108721 is about 962.2994361656.

The spelling of 891108721 in words is "eight hundred ninety-one million, one hundred eight thousand, seven hundred twenty-one".