81508561236 has 36 divisors (see below), whose sum is σ = 206044305012. Its totient is φ = 27168363264.

The previous prime is 81508561207. The next prime is 81508561241. The reversal of 81508561236 is 63216580518.

81508561236 is a `hidden beast` number, since 8 + 1 + 50 + 8 + 561 + 2 + 36 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 21478661136 + 60029900100 = 146556^2 + 245010^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a junction number, because it is equal to n+sod(n) for n = 81508561191 and 81508561200.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1427590 + ... + 1483586.

It is an arithmetic number, because the mean of its divisors is an integer number (5723452917).

Almost surely, 2^81508561236 is an apocalyptic number.

It is an amenable number.

81508561236 is an abundant number, since it is smaller than the sum of its proper divisors (124535743776).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81508561236 is a wasteful number, since it uses less digits than its factorization.

81508561236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96440 (or 96435 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 45.

The spelling of 81508561236 in words is "eighty-one billion, five hundred eight million, five hundred sixty-one thousand, two hundred thirty-six".