81636099525 has 18 divisors (see below), whose sum is σ = 146219325330. Its totient is φ = 43539252960.

The previous prime is 81636099511. The next prime is 81636099529. The reversal of 81636099525 is 52599063618.

It is a happy number.

81636099525 is a `hidden beast` number, since 8 + 1 + 6 + 3 + 609 + 9 + 5 + 25 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 12277083204 + 69359016321 = 110802^2 + 263361^2 .

It is not a de Polignac number, because 81636099525 - 2²⁶ = 81568990661 is a prime.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81636099529) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 181413330 + ... + 181413779.

Almost surely, 2^81636099525 is an apocalyptic number.

It is an amenable number.

81636099525 is a deficient number, since it is larger than the sum of its proper divisors (64583225805).

81636099525 is a wasteful number, since it uses less digits than its factorization.

81636099525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 362827125 (or 362827117 counting only the distinct ones).

The product of its (nonzero) digits is 3499200, while the sum is 54.

The spelling of 81636099525 in words is "eighty-one billion, six hundred thirty-six million, ninety-nine thousand, five hundred twenty-five".