81635643 has 6 divisors (see below), whose sum is σ = 117918164. Its totient is φ = 54423756.

The previous prime is 81635623. The next prime is 81635669. The reversal of 81635643 is 34653618.

81635643 is a `hidden beast` number, since 8 + 1 + 6 + 3 + 5 + 643 = 666.

It is not a de Polignac number, because 81635643 - 2⁹ = 81635131 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81635598 and 81635607.

It is not an unprimeable number, because it can be changed into a prime (81635623) 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, 4535305 + ... + 4535322.

Almost surely, 2^81635643 is an apocalyptic number.

81635643 is a deficient number, since it is larger than the sum of its proper divisors (36282521).

81635643 is a wasteful number, since it uses less digits than its factorization.

81635643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9070633 (or 9070630 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 81635643 is about 9035.2444903279. The cubic root of 81635643 is about 433.8037206978.

The spelling of 81635643 in words is "eighty-one million, six hundred thirty-five thousand, six hundred forty-three".