81885021 has 4 divisors (see below), whose sum is σ = 109180032. Its totient is φ = 54590012.

The previous prime is 81885019. The next prime is 81885059. The reversal of 81885021 is 12058818.

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 81885021 - 2¹ = 81885019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81885121) 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, 13647501 + ... + 13647506.

It is an arithmetic number, because the mean of its divisors is an integer number (27295008).

Almost surely, 2^81885021 is an apocalyptic number.

It is an amenable number.

81885021 is a deficient number, since it is larger than the sum of its proper divisors (27295011).

81885021 is a wasteful number, since it uses less digits than its factorization.

81885021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27295010.

The product of its (nonzero) digits is 5120, while the sum is 33.

The square root of 81885021 is about 9049.0342578642. The cubic root of 81885021 is about 434.2449950023.

The spelling of 81885021 in words is "eighty-one million, eight hundred eighty-five thousand, twenty-one".