81636523 has 4 divisors (see below), whose sum is σ = 81714528. Its totient is φ = 81558520.

The previous prime is 81636517. The next prime is 81636563. The reversal of 81636523 is 32563618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 32563618 = 2 ⋅16281809.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81636523 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81636563) 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, 37411 + ... + 39532.

It is an arithmetic number, because the mean of its divisors is an integer number (20428632).

Almost surely, 2^81636523 is an apocalyptic number.

81636523 is a deficient number, since it is larger than the sum of its proper divisors (78005).

81636523 is a wasteful number, since it uses less digits than its factorization.

81636523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78004.

The product of its digits is 25920, while the sum is 34.

The square root of 81636523 is about 9035.2931883808. The cubic root of 81636523 is about 433.8052794365.

The spelling of 81636523 in words is "eighty-one million, six hundred thirty-six thousand, five hundred twenty-three".