81658365381 has 32 divisors (see below), whose sum is σ = 121652044800. Its totient is φ = 54134846640.

The previous prime is 81658365377. The next prime is 81658365479. The reversal of 81658365381 is 18356385618.

81658365381 is a `hidden beast` number, since 8 + 1 + 6 + 583 + 6 + 53 + 8 + 1 = 666.

It is not a de Polignac number, because 81658365381 - 2² = 81658365377 is a prime.

It is a super-2 number, since 2×81658365381² (a number of 23 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81658365311) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7508910 + ... + 7519776.

It is an arithmetic number, because the mean of its divisors is an integer number (3801626400).

Almost surely, 2^81658365381 is an apocalyptic number.

It is an amenable number.

81658365381 is a deficient number, since it is larger than the sum of its proper divisors (39993679419).

81658365381 is a wasteful number, since it uses less digits than its factorization.

81658365381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12406 (or 12400 counting only the distinct ones).

The product of its digits is 4147200, while the sum is 54.

The spelling of 81658365381 in words is "eighty-one billion, six hundred fifty-eight million, three hundred sixty-five thousand, three hundred eighty-one".