81641893 has 6 divisors (see below), whose sum is σ = 82501746. Its totient is φ = 80790912.

The previous prime is 81641891. The next prime is 81641897. The reversal of 81641893 is 39814618.

It can be written as a sum of positive squares in 3 ways, for example, as 3814209 + 77827684 = 1953^2 + 8822^2 .

It is not a de Polignac number, because 81641893 - 2¹ = 81641891 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81641891) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5071 + ... + 13747.

It is an arithmetic number, because the mean of its divisors is an integer number (13750291).

Almost surely, 2^81641893 is an apocalyptic number.

It is an amenable number.

81641893 is a deficient number, since it is larger than the sum of its proper divisors (859853).

81641893 is an frugal number, since it uses more digits than its factorization.

81641893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8871 (or 8774 counting only the distinct ones).

The product of its digits is 41472, while the sum is 40.

The square root of 81641893 is about 9035.5903514934. The cubic root of 81641893 is about 433.8147910423.

The spelling of 81641893 in words is "eighty-one million, six hundred forty-one thousand, eight hundred ninety-three".