81943893 has 20 divisors (see below), whose sum is σ = 129612780. Its totient is φ = 51414912.

The previous prime is 81943877. The next prime is 81943907. The reversal of 81943893 is 39834918.

It can be written as a sum of positive squares in 2 ways, for example, as 29844369 + 52099524 = 5463^2 + 7218^2 .

It is not a de Polignac number, because 81943893 - 2⁴ = 81943877 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81943843) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 28378 + ... + 31131.

It is an arithmetic number, because the mean of its divisors is an integer number (6480639).

Almost surely, 2^81943893 is an apocalyptic number.

It is an amenable number.

81943893 is a deficient number, since it is larger than the sum of its proper divisors (47668887).

81943893 is a wasteful number, since it uses less digits than its factorization.

81943893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59538 (or 59529 counting only the distinct ones).

The product of its digits is 186624, while the sum is 45.

The square root of 81943893 is about 9052.2866172034. The cubic root of 81943893 is about 434.3490382358.

The spelling of 81943893 in words is "eighty-one million, nine hundred forty-three thousand, eight hundred ninety-three".