81511540728 has 32 divisors (see below), whose sum is σ = 205128389760. Its totient is φ = 26990575200.

The previous prime is 81511540723. The next prime is 81511540739. The reversal of 81511540728 is 82704511518.

It is a self number, because there is not a number n which added to its sum of digits gives 81511540728.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81511540723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11242450 + ... + 11249697.

It is an arithmetic number, because the mean of its divisors is an integer number (6410262180).

Almost surely, 2^81511540728 is an apocalyptic number.

It is an amenable number.

81511540728 is an abundant number, since it is smaller than the sum of its proper divisors (123616849032).

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

81511540728 is a wasteful number, since it uses less digits than its factorization.

81511540728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22492307 (or 22492303 counting only the distinct ones).

The product of its (nonzero) digits is 89600, while the sum is 42.

The spelling of 81511540728 in words is "eighty-one billion, five hundred eleven million, five hundred forty thousand, seven hundred twenty-eight".