81421979688 has 384 divisors, whose sum is σ = 275464800000. Its totient is φ = 21199159296.

The previous prime is 81421979687. The next prime is 81421979693. The reversal of 81421979688 is 88697912418.

81421979688 is a `hidden beast` number, since 81 + 421 + 9 + 79 + 68 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (81421979687) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 124688770 + ... + 124689422.

It is an arithmetic number, because the mean of its divisors is an integer number (717356250).

Almost surely, 2^81421979688 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 81421979688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137732400000).

81421979688 is an abundant number, since it is smaller than the sum of its proper divisors (194042820312).

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

81421979688 is a wasteful number, since it uses less digits than its factorization.

81421979688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1169 (or 1162 counting only the distinct ones).

The product of its digits is 13934592, while the sum is 63.

The spelling of 81421979688 in words is "eighty-one billion, four hundred twenty-one million, nine hundred seventy-nine thousand, six hundred eighty-eight".