81821998648 has 64 divisors (see below), whose sum is σ = 175044330720. Its totient is φ = 35520614400.

The previous prime is 81821998637. The next prime is 81821998651. The reversal of 81821998648 is 84689912818.

It is a self number, because there is not a number n which added to its sum of digits gives 81821998648.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3029283 + ... + 3056173.

Almost surely, 2^81821998648 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81821998648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (87522165360).

81821998648 is an abundant number, since it is smaller than the sum of its proper divisors (93222332072).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81821998648 is a wasteful number, since it uses less digits than its factorization.

81821998648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28648 (or 28644 counting only the distinct ones).

The product of its digits is 15925248, while the sum is 64.

The spelling of 81821998648 in words is "eighty-one billion, eight hundred twenty-one million, nine hundred ninety-eight thousand, six hundred forty-eight".