21073645728 has 72 divisors (see below), whose sum is σ = 59942200500. Its totient is φ = 7022905344.

The previous prime is 21073645699. The next prime is 21073645753. The reversal of 21073645728 is 82754637012.

21073645728 is a `hidden beast` number, since 2 + 1 + 0 + 73 + 6 + 4 + 572 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 20767115664 + 306530064 = 144108^2 + 17508^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2377048 + ... + 2385896.

Almost surely, 2^21073645728 is an apocalyptic number.

It is an amenable number.

21073645728 is an abundant number, since it is smaller than the sum of its proper divisors (38868554772).

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

21073645728 is a wasteful number, since it uses less digits than its factorization.

21073645728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17134 (or 17123 counting only the distinct ones).

The product of its (nonzero) digits is 564480, while the sum is 45.

The spelling of 21073645728 in words is "twenty-one billion, seventy-three million, six hundred forty-five thousand, seven hundred twenty-eight".