81751728 has 40 divisors (see below), whose sum is σ = 213875200. Its totient is φ = 26904384.

The previous prime is 81751711. The next prime is 81751777. The reversal of 81751728 is 82715718.

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, 6988 + ... + 14571.

It is an arithmetic number, because the mean of its divisors is an integer number (5346880).

Almost surely, 2^81751728 is an apocalyptic number.

It is an amenable number.

81751728 is an abundant number, since it is smaller than the sum of its proper divisors (132123472).

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

81751728 is a wasteful number, since it uses less digits than its factorization.

81751728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21649 (or 21643 counting only the distinct ones).

The product of its digits is 31360, while the sum is 39.

The square root of 81751728 is about 9041.6662181259. Note that the first 3 decimals coincide. The cubic root of 81751728 is about 434.0092447081.

The spelling of 81751728 in words is "eighty-one million, seven hundred fifty-one thousand, seven hundred twenty-eight".