2181278728 has 8 divisors (see below), whose sum is σ = 4089897630. Its totient is φ = 1090639360.

The previous prime is 2181278713. The next prime is 2181278731. The reversal of 2181278728 is 8278721812.

It can be written as a sum of positive squares in only one way, i.e., 1859506884 + 321771844 = 43122^2 + 17938^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (46) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 136329913 + ... + 136329928.

Almost surely, 2^2181278728 is an apocalyptic number.

It is an amenable number.

2181278728 is a deficient number, since it is larger than the sum of its proper divisors (1908618902).

2181278728 is a wasteful number, since it uses less digits than its factorization.

2181278728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272659847 (or 272659843 counting only the distinct ones).

The product of its digits is 200704, while the sum is 46.

The square root of 2181278728 is about 46704.1617845776. The cubic root of 2181278728 is about 1296.8917315250.

The spelling of 2181278728 in words is "two billion, one hundred eighty-one million, two hundred seventy-eight thousand, seven hundred twenty-eight".