81407728 has 40 divisors (see below), whose sum is σ = 162489600. Its totient is φ = 39493824.

The previous prime is 81407707. The next prime is 81407743. The reversal of 81407728 is 82770418.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77833 + ... + 78871.

It is an arithmetic number, because the mean of its divisors is an integer number (4062240).

Almost surely, 2^81407728 is an apocalyptic number.

It is an amenable number.

81407728 is a deficient number, since it is larger than the sum of its proper divisors (81081872).

81407728 is a wasteful number, since it uses less digits than its factorization.

81407728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1189 (or 1183 counting only the distinct ones).

The product of its (nonzero) digits is 25088, while the sum is 37.

The square root of 81407728 is about 9022.6231219086. The cubic root of 81407728 is about 433.3996385062.

The spelling of 81407728 in words is "eighty-one million, four hundred seven thousand, seven hundred twenty-eight".