81947928821 has 32 divisors (see below), whose sum is σ = 96578853120. Its totient is φ = 68746585600.

The previous prime is 81947928781. The next prime is 81947928863. The reversal of 81947928821 is 12882974918.

It is not a de Polignac number, because 81947928821 - 2²² = 81943734517 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81947988821) 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, 10950401 + ... + 10957881.

It is an arithmetic number, because the mean of its divisors is an integer number (3018089160).

Almost surely, 2^81947928821 is an apocalyptic number.

It is an amenable number.

81947928821 is a deficient number, since it is larger than the sum of its proper divisors (14630924299).

81947928821 is a wasteful number, since it uses less digits than its factorization.

81947928821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9037.

The product of its digits is 4644864, while the sum is 59.

The spelling of 81947928821 in words is "eighty-one billion, nine hundred forty-seven million, nine hundred twenty-eight thousand, eight hundred twenty-one".