891621444881 has 4 divisors (see below), whose sum is σ = 893251466352. Its totient is φ = 889991423412.

The previous prime is 891621444863. The next prime is 891621444919. The reversal of 891621444881 is 188444126198.

891621444881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also an emirpimes, since its reverse is a distinct semiprime: 188444126198 = 2 ⋅94222063099.

It is a cyclic number.

It is not a de Polignac number, because 891621444881 - 2³⁸ = 616743537937 is a prime.

It is a super-2 number, since 2×891621444881² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (891621444481) 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, 815009915 + ... + 815011008.

It is an arithmetic number, because the mean of its divisors is an integer number (223312866588).

Almost surely, 2^891621444881 is an apocalyptic number.

It is an amenable number.

891621444881 is a deficient number, since it is larger than the sum of its proper divisors (1630021471).

891621444881 is a wasteful number, since it uses less digits than its factorization.

891621444881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1630021470.

The product of its digits is 3538944, while the sum is 56.

The spelling of 891621444881 in words is "eight hundred ninety-one billion, six hundred twenty-one million, four hundred forty-four thousand, eight hundred eighty-one".