81508363136 has 64 divisors (see below), whose sum is σ = 163471381200. Its totient is φ = 40480788480.

The previous prime is 81508363103. The next prime is 81508363141. The reversal of 81508363136 is 63136380518.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×81508363136² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30265406 + ... + 30268098.

Almost surely, 2^81508363136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81508363136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (81735690600).

81508363136 is an abundant number, since it is smaller than the sum of its proper divisors (81963018064).

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

81508363136 is a wasteful number, since it uses less digits than its factorization.

81508363136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4207 (or 4195 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 44.

The spelling of 81508363136 in words is "eighty-one billion, five hundred eight million, three hundred sixty-three thousand, one hundred thirty-six".