891110021 has 4 divisors (see below), whose sum is σ = 905718444. Its totient is φ = 876501600.

The previous prime is 891109993. The next prime is 891110047. The reversal of 891110021 is 120011198.

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

It can be written as a sum of positive squares in 2 ways, for example, as 326524900 + 564585121 = 18070^2 + 23761^2 .

It is a cyclic number.

It is not a de Polignac number, because 891110021 - 2¹⁰ = 891108997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (891140021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7304120 + ... + 7304241.

It is an arithmetic number, because the mean of its divisors is an integer number (226429611).

Almost surely, 2^891110021 is an apocalyptic number.

It is an amenable number.

891110021 is a deficient number, since it is larger than the sum of its proper divisors (14608423).

891110021 is a wasteful number, since it uses less digits than its factorization.

891110021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14608422.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 891110021 is about 29851.4659774022. The cubic root of 891110021 is about 962.2999041177.

The spelling of 891110021 in words is "eight hundred ninety-one million, one hundred ten thousand, twenty-one".