81641839 has 4 divisors (see below), whose sum is σ = 82675360. Its totient is φ = 80608320.

The previous prime is 81641831. The next prime is 81641843. The reversal of 81641839 is 93814618.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81641839 - 2³ = 81641831 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 (81641831) 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, 516642 + ... + 516799.

It is an arithmetic number, because the mean of its divisors is an integer number (20668840).

Almost surely, 2^81641839 is an apocalyptic number.

81641839 is a deficient number, since it is larger than the sum of its proper divisors (1033521).

81641839 is a wasteful number, since it uses less digits than its factorization.

81641839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1033520.

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

The square root of 81641839 is about 9035.5873633096. The cubic root of 81641839 is about 433.8146953969.

The spelling of 81641839 in words is "eighty-one million, six hundred forty-one thousand, eight hundred thirty-nine".