81573893 has 4 divisors (see below), whose sum is σ = 85120608. Its totient is φ = 78027180.

The previous prime is 81573857. The next prime is 81573913. The reversal of 81573893 is 39837518.

It is a happy number.

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 a de Polignac number, because none of the positive numbers 2^k-81573893 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81570893) 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, 1773323 + ... + 1773368.

It is an arithmetic number, because the mean of its divisors is an integer number (21280152).

Almost surely, 2^81573893 is an apocalyptic number.

It is an amenable number.

81573893 is a deficient number, since it is larger than the sum of its proper divisors (3546715).

81573893 is a wasteful number, since it uses less digits than its factorization.

81573893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3546714.

The product of its digits is 181440, while the sum is 44.

The square root of 81573893 is about 9031.8266701703. The cubic root of 81573893 is about 433.6943153136.

The spelling of 81573893 in words is "eighty-one million, five hundred seventy-three thousand, eight hundred ninety-three".