81537690568 has 8 divisors (see below), whose sum is σ = 152883169830. Its totient is φ = 40768845280.

The previous prime is 81537690557. The next prime is 81537690593. The reversal of 81537690568 is 86509673518.

It can be written as a sum of positive squares in only one way, i.e., 75822028164 + 5715662404 = 275358^2 + 75602^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5096105653 + ... + 5096105668.

Almost surely, 2^81537690568 is an apocalyptic number.

It is an amenable number.

81537690568 is a deficient number, since it is larger than the sum of its proper divisors (71345479262).

81537690568 is a wasteful number, since it uses less digits than its factorization.

81537690568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10192211327 (or 10192211323 counting only the distinct ones).

The product of its (nonzero) digits is 10886400, while the sum is 58.

The spelling of 81537690568 in words is "eighty-one billion, five hundred thirty-seven million, six hundred ninety thousand, five hundred sixty-eight".