81635787904 has 128 divisors (see below), whose sum is σ = 187227936000. Its totient is φ = 35065451520.

The previous prime is 81635787899. The next prime is 81635787949. The reversal of 81635787904 is 40978753618.

It is a tau number, because it is divible by the number of its divisors (128).

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, 11205447 + ... + 11212729.

It is an arithmetic number, because the mean of its divisors is an integer number (1462718250).

Almost surely, 2^81635787904 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 81635787904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93613968000).

81635787904 is an abundant number, since it is smaller than the sum of its proper divisors (105592148096).

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

81635787904 is a wasteful number, since it uses less digits than its factorization.

81635787904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7746 (or 7734 counting only the distinct ones).

The product of its (nonzero) digits is 10160640, while the sum is 58.

The spelling of 81635787904 in words is "eighty-one billion, six hundred thirty-five million, seven hundred eighty-seven thousand, nine hundred four".