81537739728 has 20 divisors (see below), whose sum is σ = 210639161088. Its totient is φ = 27179246560.

The previous prime is 81537739687. The next prime is 81537739807. The reversal of 81537739728 is 82793773518.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 849351408 + ... + 849351503.

Almost surely, 2^81537739728 is an apocalyptic number.

It is an amenable number.

81537739728 is an abundant number, since it is smaller than the sum of its proper divisors (129101421360).

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

81537739728 is a wasteful number, since it uses less digits than its factorization.

81537739728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1698702922 (or 1698702916 counting only the distinct ones).

The product of its digits is 17781120, while the sum is 60.

The spelling of 81537739728 in words is "eighty-one billion, five hundred thirty-seven million, seven hundred thirty-nine thousand, seven hundred twenty-eight".