18331578728 has 16 divisors (see below), whose sum is σ = 34622600580. Its totient is φ = 9098885248.

The previous prime is 18331578697. The next prime is 18331578731. The reversal of 18331578728 is 82787513381.

It can be written as a sum of positive squares in 2 ways, for example, as 16895320324 + 1436258404 = 129982^2 + 37898^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 18331578728.

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, 8361851 + ... + 8364042.

Almost surely, 2^18331578728 is an apocalyptic number.

It is an amenable number.

18331578728 is a deficient number, since it is larger than the sum of its proper divisors (16291021852).

18331578728 is a wasteful number, since it uses less digits than its factorization.

18331578728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16726036 (or 16726032 counting only the distinct ones).

The product of its digits is 2257920, while the sum is 53.

The spelling of 18331578728 in words is "eighteen billion, three hundred thirty-one million, five hundred seventy-eight thousand, seven hundred twenty-eight".