81691920484 has 12 divisors (see below), whose sum is σ = 142964810604. Its totient is φ = 40844831744.

The previous prime is 81691920481. The next prime is 81691920503. The reversal of 81691920484 is 48402919618.

It can be written as a sum of positive squares in 2 ways, for example, as 42713315584 + 38978604900 = 206672^2 + 197430^2 .

It is not an unprimeable number, because it can be changed into a prime (81691920481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107197 + ... + 418180.

It is an arithmetic number, because the mean of its divisors is an integer number (11913734217).

Almost surely, 2^81691920484 is an apocalyptic number.

It is an amenable number.

81691920484 is a deficient number, since it is larger than the sum of its proper divisors (61272890120).

81691920484 is a wasteful number, since it uses less digits than its factorization.

81691920484 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 564254 (or 564252 counting only the distinct ones).

The product of its (nonzero) digits is 995328, while the sum is 52.

The spelling of 81691920484 in words is "eighty-one billion, six hundred ninety-one million, nine hundred twenty thousand, four hundred eighty-four".