81696387021 has 16 divisors (see below), whose sum is σ = 114388531584. Its totient is φ = 51764416704.

The previous prime is 81696387001. The next prime is 81696387049. The reversal of 81696387021 is 12078369618.

It is not a de Polignac number, because 81696387021 - 2⁹ = 81696386509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81696387001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3759886 + ... + 3781551.

It is an arithmetic number, because the mean of its divisors is an integer number (7149283224).

Almost surely, 2^81696387021 is an apocalyptic number.

It is an amenable number.

81696387021 is a deficient number, since it is larger than the sum of its proper divisors (32692144563).

81696387021 is a wasteful number, since it uses less digits than its factorization.

81696387021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7541620.

The product of its (nonzero) digits is 870912, while the sum is 51.

The spelling of 81696387021 in words is "eighty-one billion, six hundred ninety-six million, three hundred eighty-seven thousand, twenty-one".