81137864 has 8 divisors (see below), whose sum is σ = 152133510. Its totient is φ = 40568928.

The previous prime is 81137857. The next prime is 81137879. The reversal of 81137864 is 46873118.

It can be written as a sum of positive squares in only one way, i.e., 63075364 + 18062500 = 7942^2 + 4250^2 .

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, 5071109 + ... + 5071124.

Almost surely, 2^81137864 is an apocalyptic number.

It is an amenable number.

81137864 is a deficient number, since it is larger than the sum of its proper divisors (70995646).

81137864 is a wasteful number, since it uses less digits than its factorization.

81137864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10142239 (or 10142235 counting only the distinct ones).

The product of its digits is 32256, while the sum is 38.

The square root of 81137864 is about 9007.6558548826. The cubic root of 81137864 is about 432.9202063939.

The spelling of 81137864 in words is "eighty-one million, one hundred thirty-seven thousand, eight hundred sixty-four".