81820900161 has 72 divisors (see below), whose sum is σ = 161516706624. Its totient is φ = 39234767040.

The previous prime is 81820900153. The next prime is 81820900181. The reversal of 81820900161 is 16100902818.

It is not a de Polignac number, because 81820900161 - 2³ = 81820900153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81820900111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 585661 + ... + 711786.

It is an arithmetic number, because the mean of its divisors is an integer number (2243287592).

Almost surely, 2^81820900161 is an apocalyptic number.

It is an amenable number.

81820900161 is a deficient number, since it is larger than the sum of its proper divisors (79695806463).

81820900161 is a wasteful number, since it uses less digits than its factorization.

81820900161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1297491 (or 1297481 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 36.

The spelling of 81820900161 in words is "eighty-one billion, eight hundred twenty million, nine hundred thousand, one hundred sixty-one".