81533959938 has 20 divisors (see below), whose sum is σ = 182696466150. Its totient is φ = 27177986592.

The previous prime is 81533959933. The next prime is 81533959973. The reversal of 81533959938 is 83995933518.

81533959938 is a `hidden beast` number, since 8 + 1 + 5 + 3 + 3 + 9 + 599 + 38 = 666.

It can be written as a sum of positive squares in only one way, i.e., 45700605729 + 35833354209 = 213777^2 + 189297^2 .

It is not an unprimeable number, because it can be changed into a prime (81533959933) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 251647863 + ... + 251648186.

Almost surely, 2^81533959938 is an apocalyptic number.

81533959938 is an abundant number, since it is smaller than the sum of its proper divisors (101162506212).

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

81533959938 is a wasteful number, since it uses less digits than its factorization.

81533959938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503296063 (or 503296054 counting only the distinct ones).

The product of its digits is 31492800, while the sum is 63.

The spelling of 81533959938 in words is "eighty-one billion, five hundred thirty-three million, nine hundred fifty-nine thousand, nine hundred thirty-eight".