81856210005 has 24 divisors (see below), whose sum is σ = 141899778072. Its totient is φ = 43651820544.

The previous prime is 81856209991. The next prime is 81856210021. The reversal of 81856210005 is 50001265818.

81856210005 is a `hidden beast` number, since 81 + 8 + 562 + 10 + 0 + 0 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 5259005361 + 76597204644 = 72519^2 + 276762^2 .

It is not a de Polignac number, because 81856210005 - 2⁴ = 81856209989 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 331597 + ... + 523133.

It is an arithmetic number, because the mean of its divisors is an integer number (5912490753).

Almost surely, 2^81856210005 is an apocalyptic number.

It is an amenable number.

81856210005 is a deficient number, since it is larger than the sum of its proper divisors (60043568067).

81856210005 is a wasteful number, since it uses less digits than its factorization.

81856210005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201045 (or 201042 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 36.

The spelling of 81856210005 in words is "eighty-one billion, eight hundred fifty-six million, two hundred ten thousand, five".