81540728 has 32 divisors (see below), whose sum is σ = 157172400. Its totient is φ = 39637248.

The previous prime is 81540707. The next prime is 81540769. The reversal of 81540728 is 82704518.

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, 100388 + ... + 101196.

Almost surely, 2^81540728 is an apocalyptic number.

It is an amenable number.

81540728 is a deficient number, since it is larger than the sum of its proper divisors (75631672).

81540728 is a wasteful number, since it uses less digits than its factorization.

81540728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1151 (or 1147 counting only the distinct ones).

The product of its (nonzero) digits is 17920, while the sum is 35.

The square root of 81540728 is about 9029.9904761855. The cubic root of 81540728 is about 433.6355325293.

The spelling of 81540728 in words is "eighty-one million, five hundred forty thousand, seven hundred twenty-eight".