21704718728 has 32 divisors (see below), whose sum is σ = 50738304960. Its totient is φ = 8456383680.

The previous prime is 21704718701. The next prime is 21704718767. The reversal of 21704718728 is 82781740712.

It is a happy number.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17616851 + ... + 17618082.

It is an arithmetic number, because the mean of its divisors is an integer number (1585572030).

Almost surely, 2^21704718728 is an apocalyptic number.

21704718728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21704718728 is an abundant number, since it is smaller than the sum of its proper divisors (29033586232).

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

21704718728 is a wasteful number, since it uses less digits than its factorization.

21704718728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35234957 (or 35234953 counting only the distinct ones).

The product of its (nonzero) digits is 351232, while the sum is 47.

The spelling of 21704718728 in words is "twenty-one billion, seven hundred four million, seven hundred eighteen thousand, seven hundred twenty-eight".