81657868642 has 8 divisors (see below), whose sum is σ = 139984917696. Its totient is φ = 34996229412.

The previous prime is 81657868639. The next prime is 81657868673. The reversal of 81657868642 is 24686875618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×81657868642² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2916352438 + ... + 2916352465.

It is an arithmetic number, because the mean of its divisors is an integer number (17498114712).

Almost surely, 2^81657868642 is an apocalyptic number.

81657868642 is a deficient number, since it is larger than the sum of its proper divisors (58327049054).

81657868642 is a wasteful number, since it uses less digits than its factorization.

81657868642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5832704912.

The product of its digits is 30965760, while the sum is 61.

The spelling of 81657868642 in words is "eighty-one billion, six hundred fifty-seven million, eight hundred sixty-eight thousand, six hundred forty-two".