81438911136 has 432 divisors, whose sum is σ = 265154329440. Its totient is φ = 24416017920.

The previous prime is 81438911089. The next prime is 81438911143. The reversal of 81438911136 is 63111983418.

81438911136 is a `hidden beast` number, since 81 + 438 + 9 + 1 + 1 + 136 = 666.

It is a tau number, because it is divible by the number of its divisors (432).

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

It is a junction number, because it is equal to n+sod(n) for n = 81438911091 and 81438911100.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 413395390 + ... + 413395586.

It is an arithmetic number, because the mean of its divisors is an integer number (613783170).

Almost surely, 2^81438911136 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 81438911136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132577164720).

81438911136 is an abundant number, since it is smaller than the sum of its proper divisors (183715418304).

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

81438911136 is a wasteful number, since it uses less digits than its factorization.

81438911136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 421 (or 392 counting only the distinct ones).

The product of its digits is 124416, while the sum is 45.

The spelling of 81438911136 in words is "eighty-one billion, four hundred thirty-eight million, nine hundred eleven thousand, one hundred thirty-six".