891021861 has 12 divisors (see below), whose sum is σ = 1287811200. Its totient is φ = 593654760.

The previous prime is 891021851. The next prime is 891021869. The reversal of 891021861 is 168120198.

It is not a de Polignac number, because 891021861 - 2⁶ = 891021797 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (891021869) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13845 + ... + 44426.

It is an arithmetic number, because the mean of its divisors is an integer number (107317600).

Almost surely, 2^891021861 is an apocalyptic number.

It is an amenable number.

891021861 is a deficient number, since it is larger than the sum of its proper divisors (396789339).

891021861 is a wasteful number, since it uses less digits than its factorization.

891021861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59976 (or 59973 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 36.

The square root of 891021861 is about 29849.9892964805. The cubic root of 891021861 is about 962.2681687333.

The spelling of 891021861 in words is "eight hundred ninety-one million, twenty-one thousand, eight hundred sixty-one".